CN115377385A - Bulk phase doped ternary cathode material with surface coated with lithium ion conductor and preparation method and application thereof - Google Patents
Bulk phase doped ternary cathode material with surface coated with lithium ion conductor and preparation method and application thereof Download PDFInfo
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- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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Abstract
The invention provides a bulk phase doping ternary cathode material with a surface coated with a lithium ion conductor, and a preparation method and application thereof, and belongs to the technical field of cathode materials of lithium ion batteries. According to the invention, nickel and cobalt elements are used as a matrix, molybdenum or tungsten elements are blended in by a coprecipitation method, and in the subsequent lithium mixing sintering process, the molybdenum or tungsten elements are blended in the subsurface layer of the primary particles of the matrix of the anode material, so that the surface energy of the primary particles is changed, and the primary grains with large length-diameter ratio and thinning and more crystal boundaries are formed on the surface of the anode material, thereby being beneficial to relieving the internal micro-stress of the secondary particles. Meanwhile, the fusion of molybdenum or tungsten elements can enable cations on the sub-surface layer of the primary particles of the cathode material to be orderly arranged, in the processes of hydrolysis and subsequent high-temperature sintering, part of doping elements of the surface lithium ion conductor precursor coating layer are fused into the bulk phase of the cathode material, and part of the doping elements react with a lithium source to form a compact lithium ion conductor coating layer, so that the stability of the bulk phase and the surface structure of the cathode material is improved, and the electrochemical stability of the ternary cathode material is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a bulk phase doping ternary anode material with a surface coated with a lithium ion conductor, and a preparation method and application thereof.
Background
With the requirement of the new energy automobile market on the endurance mileage being higher and higher, the lithium ion power battery is continuously developed to the direction of higher energy density, which requires that the positive electrode material also has higher energy density. However, the ternary cathode materials that have been commercialized to date have failed to meet the energy density requirements of lithium ion power batteries. The energy density of the ternary cathode material can be improved by increasing the content of the nickel element, so that the energy density of the power battery is improved. But the cycle stability and thermal stability become worse due to a large increase in nickel content, compared to the mature ternary cathode material that has been commercialized so far.
The bulk phase doping is combined with the surface coating modification, so that the electrochemical performance and the safety performance of the high-nickel ternary cathode material can be further improved. However, the current doping and coating dual modification processes are performed independently, for example, patent CN109879331A discloses a method of mixing a hydroxide precursor of a ternary cathode material, a lithium source and an oxide of a doping element, then sintering the mixture at a high temperature and a solid phase, preparing a doped ternary cathode material, and then synthesizing a lithium phosphate ion conductor (Li) by a sol-gel method or a high temperature and solid phase method 1+a A a D 2-a (PO 4 ) 3 Preparing a ternary cathode material which is doped with bulk multi-elements and coated with a phosphate lithium ion conductor on the surface by high-temperature sintering; patent CN108878799A discloses a method of obtaining a doped lithium nickel cobalt manganese oxide ternary positive electrode material by in-situ doping coprecipitation-high temperature solid phase method, and then coating a mesoporous lithium aluminum silicate coating layer with high-speed lithium ions and electronic channels on the surface of the doped positive electrode material by template-sol/gel-low temperature tempering process to prepare a bulk phase doped multi-element and surface coated mesoporous lithium aluminum silicate lithium ion conductor (LiAlSi) 2 O 6 ) Ternary of (2)And (3) a positive electrode material. However, the above schemes of doping and coating respectively have the defects of complicated process and unstable structure of the obtained product, which results in poor electrochemical stability of the ternary cathode material.
Disclosure of Invention
In view of the above, the present invention aims to provide a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, and a preparation method and an application thereof, wherein the method is simple, and the obtained ternary cathode material has good structural stability and high electrochemical stability.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, which comprises the following steps:
mixing soluble nickel salt, soluble cobalt salt and water to obtain a mixed salt solution; the molar ratio of nickel ions to cobalt ions in the mixed salt solution is 0.9-1;
mixing the mixed salt solution, a VIB group metal source, a precipitator, a complexing agent and water, and carrying out coprecipitation reaction to obtain a hydroxide precursor, wherein the VIB group metal source is a molybdenum source or a tungsten source;
mixing the hydroxide precursor, soluble salt of the doping element and a solvent, and performing hydrolysis reaction to obtain a hydroxide precursor with the surface coated with a lithium ion conductor precursor; the doping element is one or more of B, ti, al, nb, sb, sn, si, ge and Zr; the solvent is water and/or alcohol;
heating and oxidizing the hydroxide precursor coated with the lithium ion conductor precursor on the surface to obtain an oxide precursor;
and mixing the oxide precursor with lithium salt, and sintering to obtain the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor.
Preferably, the precipitator is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate;
the complexing agent is one or more of ammonia water, disodium ethylene diamine tetraacetate, citric acid, sodium citrate, oxalic acid and sodium oxalate.
Preferably, the molar ratio of the total metal ions in the mixed salt solution to the group VIB metal ions in the group VIB metal source is 0.93-0.99;
the temperature of the precipitation reaction is 35-85 ℃, and the time is 5-80 h.
Preferably, the molar ratio of the total metal ions to the doping element ions in the hydroxide precursor is from 0.95 to 0.995, and from 0.005 to 0.05.
Preferably, the temperature of the hydrolysis reaction is 60-95 ℃, and the time is 1-5 h.
Preferably, the temperature of the heating oxidation is 400-600 ℃, and the time is 1-10 h.
Preferably, the molar ratio of the total metal ions in the oxide precursor to the lithium ions in the lithium salt is 1;
the sintering temperature is 600-820 ℃ and the sintering time is 10-20 h.
The invention provides a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, which is prepared by the preparation method and comprises the bulk phase doped ternary cathode material and a lithium ion conductor layer coated on the surface of the bulk phase doped ternary cathode material;
the bulk phase doped ternary cathode material comprises a ternary cathode material matrix and a doping element bulk phase doped in the ternary cathode material matrix, and the chemical composition of the ternary cathode material is LiNi x Co y Mo 1-x-y O 2 Or LiNi x Co y W 1-x-y O 2 Wherein x is more than or equal to 0.9<1.0，0.01≤y<0.1, and x + y<1；
The doping element is one or more of B, ti, al, nb, sb, sn, si, sc, Y, ge and Zr;
the chemical composition of the lithium ion conductor layer is Li 3 BO 3 、Li 2 WO 4 、Li 2 MoO 4 、Li 2 TiO 3 、LiAlO 2 、LiNbO 3 、LiSbO 3 、Li 2 SnO 3 、Li 4 SiO 4 、Li 2 GeO 3 、Li 2 ZrO 3 、Li 3 PO 4 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 1.8 Sc 0.8 Ti 1.2 (PO 4 ) 3 And Li 1.4 Y 0.4 Ti 1.6 (PO 4 ) 3 One or more of them.
Preferably, the molar ratio of the doping element to the metal element in the ternary cathode material matrix is 0.01-1;
the content of the lithium ion conductor layer in the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor is 0.1-10 wt.%.
The invention provides an application of the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor in a lithium ion power battery.
The invention provides a preparation method of a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, which comprises the following steps: mixing soluble nickel salt, soluble cobalt salt and water to obtain a mixed salt solution; the molar ratio of nickel ions to cobalt ions in the mixed salt solution is 0.9-1; mixing the mixed salt solution, a VIB group metal source, a precipitator, a complexing agent and water, and carrying out coprecipitation reaction to obtain a hydroxide precursor, wherein the VIB group metal source is a molybdenum source or a tungsten source; mixing the hydroxide precursor, soluble salt of the doping element and a solvent, and performing hydrolysis reaction to obtain a hydroxide precursor with the surface coated with a lithium ion conductor precursor; the doping element is one or more of B, ti, al, nb, sb, sn, si, ge and Zr; the solvent is water and/or alcohol; heating and oxidizing the hydroxide precursor coated with the lithium ion conductor precursor on the surface to obtain an oxide precursor; and mixing the oxide precursor with lithium salt, and sintering to obtain the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor. The method takes nickel (Ni) and cobalt (Co) elements as a matrix, uniformly fuses molybdenum (Mo) or tungsten (W) elements through a coprecipitation method, firstly, the molybdenum or tungsten elements are uniformly deposited in a nickel-cobalt-molybdenum or nickel-cobalt-tungsten hydroxide precursor in a liquid phase state, then, the lithium ion conductor precursor is uniformly coated on the surface of the nickel-cobalt-molybdenum or nickel-cobalt-tungsten hydroxide precursor through a hydrolysis method, in the subsequent lithium mixing and sintering process, the molybdenum or tungsten elements are fused into the subsurface layer of primary particles of the matrix of the anode material, the surface energy of the primary particles of the matrix of the anode material is changed, primary grains with large length-diameter ratio and more grain boundaries are formed on the surface of the anode material, and the internal micro-stress of the secondary particles is favorably relieved. Meanwhile, the fusion of molybdenum or tungsten elements can enable cations on the subsurface layer of primary particles of the matrix of the positive electrode material to be orderly arranged, in the hydrolysis process, part of doping elements of the surface lithium ion conductor precursor coating layer are fused into the bulk phase of the positive electrode material, and part of doping elements react with a lithium source to form a compact lithium ion conductor coating layer, so that the bulk phase and surface structure stability of the positive electrode material are further improved, and the electrochemical stability of the ternary positive electrode material is improved. The bulk phase doped ternary positive electrode material with the surface coated with the lithium ion conductor prepared by the invention has uniform bulk phase doping elements, and the surface lithium ion conductor coating layer is uniform and compact, so that a large number of microcracks generated in secondary spherical particles due to volume expansion of the ternary positive electrode material in the charging and discharging processes can be effectively inhibited, the corrosion of electrolyte on the ternary positive electrode material and the occurrence of side reactions can be well inhibited, and meanwhile, the lithium ion conductor coating layer can also improve the diffusivity of lithium ions on the interface of an electrode and the electrolyte, and further effectively improve the rate capability, cycle life and safety performance of the material.
Meanwhile, in the sintering process of the ternary cathode material, new elements can be doped in the bulk phase and the subsurface, and the surface of the secondary particles is coated with the lithium ion conductor coating layer, so that the method is simple to operate, and can effectively overcome the defects of complex operation, unreasonable distribution of the doped elements and unstable coating structure of the traditional method for respectively doping and coating. The method provided by the invention is green and environment-friendly, is suitable for industrial production, and is a new technology of a high-performance lithium ion battery anode material with an industrial prospect.
Drawings
FIG. 1 is an SEM image of a nickel cobalt molybdenum hydroxide precursor material coated with titanium hydroxide oxide prepared in example 1;
FIG. 2 is an SEM image of the bulk phase titanium doped lithium nickel cobalt molybdate cathode material coated with lithium metatitanate prepared in example 1;
fig. 3 is an XRD spectrogram of the bulk phase titanium doped lithium nickel cobalt molybdate cathode material coated with lithium metatitanate prepared in example 1;
fig. 4 is a first charge-discharge curve diagram of a CR2025 button cell made of a nickel-cobalt lithium molybdate anode material doped with bulk titanium and coated with lithium metatitanate on the surface, prepared in example 1 of the present invention, at a current density of 0.1C and a voltage of 2.7 to 4.3V;
fig. 5 is a graph of the rate cycle performance of a CR2025 button cell fabricated using a bulk phase titanium doped lithium nickel cobalt molybdate cathode material coated with lithium metatitanate prepared in example 1 of the present invention;
fig. 6 is a cycle curve diagram of a CR2025 button cell fabricated using a bulk titanium doped lithium nickel cobalt molybdate anode material coated with lithium metatitanate prepared in example 1 of the present invention under the conditions of a current density of 1.0C and a voltage of 2.7 to 4.3V;
FIG. 7 is an SEM image of a nickel cobalt molybdenum hydroxide precursor material coated with silicon hydroxide prepared in example 2;
FIG. 8 is an SEM image of bulk silicon doped lithium nickel cobalt molybdate cathode material coated with lithium silicate prepared in example 2;
FIG. 9 is an XRD spectrum of bulk silicon doped lithium nickel cobalt molybdate cathode material coated with lithium silicate prepared in example 2;
fig. 10 is a first charge-discharge curve diagram of a CR2025 button cell fabricated using the bulk silicon-doped lithium nickel cobalt molybdate anode material coated with lithium silicate prepared in embodiment 2 of the present invention under the conditions of current density of 0.1C and voltage of 2.7-4.3V;
fig. 11 is a graph showing the rate cycle performance of a CR2025 button cell fabricated using the bulk silicon doped lithium nickel cobalt molybdate cathode material coated with lithium silicate prepared in example 2 of the present invention;
fig. 12 is a cycle curve diagram of a CR2025 button cell fabricated using the bulk silicon doped lithium nickel cobalt molybdate anode material coated with lithium silicate prepared in example 2 of the present invention under the conditions of current density of 1.0C and voltage of 2.7-4.3V;
FIG. 13 is an SEM image of a nickel cobalt tungsten hydroxide precursor material with a surface coated with titanium hydroxide prepared in example 3;
fig. 14 is an SEM image of the lithium nickel cobalt tungstate cathode material doped with bulk titanium and coated with lithium metatitanate on the surface, prepared in example 3;
FIG. 15 is an XRD spectrum of a lithium nickel cobalt tungstate cathode material doped with bulk titanium and coated with lithium metatitanate on the surface, prepared in example 3;
fig. 16 is a first charge-discharge curve diagram of a CR2025 button cell fabricated using the bulk titanium doped lithium nickel cobalt tungstate cathode material coated with lithium metatitanate prepared in example 3 of the present invention under the conditions of current density of 0.1C and voltage of 2.7-4.3V;
fig. 17 is a graph of rate cycle performance of a CR2025 button cell fabricated using a lithium nickel cobalt tungstate positive electrode material doped with bulk phase titanium and coated with lithium metatitanate according to example 3 of the present invention;
fig. 18 is a circulation curve diagram of a CR2025 button cell fabricated using the bulk phase titanium-doped lithium nickel cobalt tungstate positive electrode material coated with lithium metatitanate prepared in example 3 of the present invention under the conditions of current density of 1.0C and voltage of 2.7-4.3V;
FIG. 19 is an SEM image of a nickel cobalt molybdenum hydroxide precursor material prepared in comparative example 1;
fig. 20 is an SEM image of the lithium nickel cobalt molybdate cathode material prepared in comparative example 1;
FIG. 21 is an XRD spectrum of the lithium nickel cobalt molybdate cathode material prepared in comparative example 1;
fig. 22 is a first charge-discharge curve diagram of a CR2025 button cell made of the lithium nickel cobalt molybdate positive electrode material prepared in comparative example 1 of the present invention under the conditions of current density of 0.1C and voltage of 2.7-4.3V;
fig. 23 is a graph of the rate cycle performance of a CR2025 button cell made using the lithium nickel cobalt molybdate positive electrode material prepared in comparative example 1 of the present invention;
fig. 24 is a cycle curve diagram of a CR2025 button cell made of the nickel cobalt lithium molybdate positive electrode material prepared in comparative example 1 according to the present invention at a current density of 1.0C and a voltage of 2.7-4.3V;
FIG. 25 is an SEM image of a nickel cobalt tungsten hydroxide precursor material prepared in comparative example 2;
fig. 26 is an SEM image of the lithium nickel cobalt tungstate positive electrode material prepared in comparative example 2;
fig. 27 is an XRD spectrum of the lithium nickel cobalt tungstate positive electrode material prepared in comparative example 2;
FIG. 28 is a first charging and discharging curve diagram of a CR2025 button cell made of the lithium nickel cobalt tungstate positive electrode material prepared in comparative example 2 of the present invention under the conditions of current density of 0.1C and voltage of 2.7-4.3V;
fig. 29 is a graph of the rate cycle performance of a CR2025 button cell made using the lithium nickel cobalt tungstate positive electrode material prepared in comparative example 2 of the present invention;
fig. 30 is a circulation curve diagram of a CR2025 button cell made of the lithium nickel cobalt tungstate positive electrode material prepared in comparative example 2 of the present invention under the conditions of current density of 1.0C and voltage of 2.7-4.3V.
Detailed Description
The invention provides a preparation method of a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, which comprises the following steps:
mixing soluble nickel salt, soluble cobalt salt and water to obtain a mixed salt solution; the molar ratio of nickel ions to cobalt ions in the mixed salt solution is 0.9-1;
mixing the mixed salt solution, a VIB group metal source, a precipitator, a complexing agent and water, and carrying out coprecipitation reaction to obtain a hydroxide precursor, wherein the VIB group metal source is a molybdenum source or a tungsten source;
mixing the hydroxide precursor, soluble salt of the doping element and a solvent, and carrying out hydrolysis reaction to obtain a hydroxide precursor with the surface coated with a lithium ion conductor precursor; the doping element is one or more of B, ti, al, nb, sb, sn, si, ge and Zr; the solvent is water and/or alcohol;
heating and oxidizing the hydroxide precursor coated with the lithium ion conductor precursor on the surface to obtain an oxide precursor;
and mixing the oxide precursor with lithium salt, and sintering to obtain the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor.
The invention mixes soluble nickel salt, soluble cobalt salt and water to obtain mixed salt solution. In the invention, the soluble nickel salt is preferably one or more of nickel sulfate, nickel nitrate and nickel acetate; the soluble cobalt salt is preferably one or more of cobalt sulfate, cobalt nitrate and cobalt acetate. In the present invention, when the soluble nickel salt or the soluble cobalt salt is two or more of the above, the ratio of the soluble nickel salt or the soluble cobalt salt of different species is not particularly limited, and any ratio may be used.
In the present invention, the molar ratio of nickel ions to cobalt ions in the mixed salt solution is 0.9 to 1, preferably 0.92 to 0.95.
The invention does not require any particular mixing means, such as stirring, known to the person skilled in the art.
In the present invention, the molar concentration of the total metal ions of nickel and cobalt in the mixed salt solution is preferably 0.3 to 3.0mol · L -1 More preferably 1.6 to 2 mol.L -1 More preferably 1.9 to 2 mol.L -1 。
After the mixed salt solution is obtained, the mixed salt solution, a VIB group metal source, a precipitator, a complexing agent and water are mixed for coprecipitation reaction, and a hydroxide precursor is obtained. In the invention, the VIB group metal source is a molybdenum source or a tungsten source. In the invention, the molybdenum source is preferably one or more of molybdenum trioxide, sodium molybdate and ammonium molybdate; the tungsten source is preferably one or more of tungsten trioxide, sodium tungstate and potassium tungstate.
In the present invention, the group VIB metal source is preferably provided in the form of an alkaline solution. In the present invention, the method for preparing the alkaline solution of the group VIB metal source preferably comprises the following steps:
mixing a VIB group metal source, inorganic base and water to obtain an alkaline solution of the VIB group metal source.
In the present invention, the inorganic base is preferably one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate. When the inorganic base is more than two of the inorganic bases, the proportion of different types of bases is not specially limited, and the inorganic base can be prepared in any proportion.
In the present invention, the mass concentration of the inorganic base in the group VIB metal source alkaline solution is preferably 1 to 20wt.%, and more preferably 5 to 8wt.%. In the invention, the concentration of the VIB group metal source in the alkaline solution of the VIB group metal source is preferably 0.01-1.5 mol.L -1 More preferably 0.25 to 0.35 mol.L -1 。
In the invention, the precipitant is preferably one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate; when the precipitating agents are more than two of the precipitating agents, the proportion of different precipitating agents is not particularly limited, and the precipitating agents can be prepared in any proportion. In the present invention, the precipitant is preferably provided in the form of a solution, and the mass concentration of the precipitant solution is preferably 1 to 40%, more preferably 5 to 10%, and still more preferably 7 to 9%.
In the invention, the complexing agent is preferably one or more of ammonia water, disodium ethylene diamine tetraacetate, citric acid, sodium citrate, oxalic acid and sodium oxalate. When the complexing agents are more than two of the complexing agents, the proportion of different complexing agents is not specially limited, and any proportion can be adopted; in the present invention, the complexing agent is preferably provided in the form of a solution, and the molar concentration of the complexing agent solution is preferably 1 to 10mol L -1 More preferably 5 to 9mol L -1 More preferably 5.5 to 6.5mol L -1 。
In the present invention, the molar ratio of the total metal ions in the mixed salt solution to the group VIB metal ions in the group VIB metal source is preferably 0.93 to 0.99, more preferably 0.01 to 0.07.
In the present invention, in the case of the present invention,after the mixed salt solution, the VIB group metal source, the precipitant, the complexing agent and the water are mixed, the molar concentration of the VIB group metal source ions in the obtained mixed solution is preferably 0.01-1.5 mol.L -1 More preferably 0.25 to 0.35 mol.L -1 。
In the present invention, the mixing is preferably performed by stirring. In the present invention, the mixing is particularly preferably:
dropping mixed salt solution, alkali solution containing molybdenum or tungsten element, precipitant solution and complexing agent solution into a stainless steel coprecipitation reaction kettle at a certain speed, continuously stirring, adjusting the dropping speed of the precipitant solution to control the pH value of the reaction solution to be 10.5-12.5, more preferably 12.2-12.3, adjusting the dropping speed of the complexing agent solution to control the concentration of the complexing agent in the reaction kettle to be 0.1-1.0 molL -1 More preferably 0.45 to 0.55mol L -1 (ii) a The dropping rate is preferably 0.5 to 50.0 mL/min -1 More preferably 1 to 20 mL/min -1 。
In the present invention, the pH value is preferably 10.5 to 12.5, more preferably 12.2 to 12.3, and the concentration of the complexing agent is preferably 0.1 to 1.0mol · L during the coprecipitation reaction -1 More preferably 0.45 to 0.55 mol.L -1 (ii) a The temperature of the coprecipitation reaction is preferably 35 to 85 ℃, more preferably 55 to 65 ℃, the stirring speed is preferably 600 to 1200rpm, more preferably 1100 to 1200rpm, and the reaction time is preferably 5 to 80 hours, more preferably 40 to 50 hours.
After the coprecipitation reaction, the present invention preferably ages the resulting coprecipitated reactant. In the present invention, the aging temperature is preferably room temperature, and the time is preferably 2 hours. After said aging, the present invention preferably subjects the resulting aged product to a post-treatment, which in the present invention preferably comprises the steps of:
and carrying out solid-liquid separation on the aged product, and washing and drying the obtained solid in sequence to obtain a hydroxide precursor solid.
In the present invention, the solid-liquid separation method is preferably suction filtration. In the present invention, the washing is preferably: the obtained solid is filtered, filtered and washed by deionized water until the pH value of the filtrate is 8.0-9.8, and more preferably 9.2-9.3. In the present invention, the drying is preferably air-blast drying; the drying temperature is preferably 80-120 ℃, and more preferably 90-100 ℃; the time is preferably 6 to 35 hours, more preferably 15 to 20 hours.
In the invention, the shape of the hydroxide precursor is spherical or sphere-like; the chemical composition of the hydroxide precursor is Ni x Co y Mo 1-x-y (OH) z Or Ni x Co y W 1-x-y (OH) z (wherein, 0.9. Ltoreq. X<1.0，0.01≤y<0.1，2≤z＜3)。
After the hydroxide precursor is obtained, the hydroxide precursor, the soluble salt of the doping element and the solvent are mixed for hydrolysis reaction to obtain the hydroxide precursor with the surface coated with the lithium ion conductor precursor. In the present invention, the hydroxide precursor is preferably provided in the form of a dispersion. In the invention, the solvent of the hydroxide precursor dispersion liquid is preferably one or more of deionized water, ethanol, ethylene glycol, propylene alcohol and isopropanol; when the solvent is more than two of the above solvents, the invention has no special limitation on the mixture ratio of different solvents, and the mixture ratio can be any. In the present invention, the mass ratio of the hydroxide precursor to the solvent in the hydroxide precursor dispersion is preferably from 1.
In the invention, the doping element is one or more of B, ti, al, nb, sb, sn, si, ge and Zr. In the invention, the soluble salt of the doping element is preferably one or more of sodium borate, titanyl sulfate, tetrabutyl titanate, aluminum sulfate, aluminum isopropoxide, ammonium niobate, sodium silicate and tetraethyl orthosilicate.
In the present invention, the solvent is water and/or alcohol. In the present invention, the alcohol is preferably one or more of ethanol, ethylene glycol, propylene alcohol and isopropyl alcohol. In the present invention, when the solvent is water and alcohol, the present invention has no particular requirement on the mass ratio of water and alcohol.
In the present invention, the soluble salt of the doping element is preferably provided in the form of a water and/or alcohol solution.
In the present invention, the mixing is preferably performed in the following manner: a solution of a soluble salt of the doping element is added to the hydroxide precursor dispersion with stirring. In the invention, the addition rate of the soluble salt solution of the doping element is preferably 0.1-1 mLmin -1 . In the present invention, the stirring rate is preferably 200 to 600rpm.
In the present invention, the molar ratio of the total metal ions to the dopant element ions in the hydroxide precursor is 0.95 to 0.995. More preferably 0.96 to 0.98.
In the present invention, the temperature of the hydrolysis reaction is preferably 60 to 95 ℃, more preferably 90 to 90 ℃; the time is preferably 1 to 5 hours, more preferably 2 to 3 hours.
After the hydrolysis reaction, the present invention preferably performs a post-treatment on the obtained hydrolysis reaction solution, and the post-treatment preferably comprises the following steps: filtering with filter paper, performing solid-liquid separation, washing with deionized water until the pH value of the filtrate is less than 9.0, and vacuum drying at 100 deg.C for 24 hr.
After obtaining the hydroxide precursor of the surface-coated lithium ion conductor precursor, the invention heats and oxidizes the hydroxide precursor of the surface-coated lithium ion conductor precursor to obtain the oxide precursor. In the present invention, the atmosphere of the thermal oxidation is preferably air. In the present invention, the temperature of the heating oxidation is preferably 400 to 600 ℃, more preferably 400 to 500 ℃; the holding time is preferably 1 to 10 hours, more preferably 3 to 5 hours.
After the heating oxidation, the oxide precursor is mixed with lithium salt and sintered to obtain the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor. In the invention, the lithium salt is preferably one or more of lithium hydroxide, lithium carbonate, lithium acetate and lithium nitrate; when the lithium salt is more than two of the above, the ratio of the lithium salts of different types is not particularly limited, and any ratio may be used.
In the present invention, the mixing is preferably performed by ball milling. In the invention, the ball milling medium for ball milling mixing is preferably polytetrafluoroethylene small balls; the diameter of the ball milling medium is preferably 1-20 mm, and more preferably 6-10 mm; the rotation speed of the ball mill is preferably 100-500 rpm, more preferably 250-300 rpm; the time is preferably 10 to 100min, more preferably 30 to 60min.
In the present invention, the sintering is preferably performed in an air or oxygen atmosphere, and the sintering temperature is preferably 600 to 820 ℃, and more preferably 690 to 730 ℃; the holding time is preferably 10 to 20 hours, more preferably 10 to 18 hours, and still more preferably 10 to 12 hours. In the present invention, the rate of temperature rise to the sintering temperature is preferably 0.5 to 10 ℃ for min -1 More preferably 0.5 to 5 ℃ for min -1 More preferably 1 to 2 ℃ for min -1 。
After sintering, the obtained sintered product is preferably crushed and graded to obtain the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor. In the present invention, the particle size of the bulk-doped ternary positive electrode material having a surface coated with a lithium ion conductor is preferably 1 to 15 μm, and more preferably 5 to 10 μm. The process of the present invention for the crushing and classifying is not particularly limited, and may be performed according to a process well known in the art.
The invention provides a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, which is prepared by the preparation method and comprises the bulk phase doped ternary cathode material and a lithium ion conductor layer coated on the surface of the bulk phase doped ternary cathode material;
the bulk phase doped ternary cathode material comprises a ternary cathode material matrix and a doping element bulk phase doped in the ternary cathode material matrix, and the chemical composition of the ternary cathode material is LiNi x Co y Mo 1-x-y O 2 Or LiNi x Co y W 1-x-y O 2 Wherein x is more than or equal to 0.9<1.0，0.01≤y<0.1; as a specific embodiment of the invention, the chemical composition of the ternary cathode material is LiNi 0.9 Co 0.09 Mo 0.01 O 2 、LiNi 0.95 Co 0.03 Mo 0.02 O 2 、LiNi 0.98 Co 0.01 Mo 0.01 O 2 、LiNi 0.9 Co 0.09 W 0.01 O 2 、LiNi 0.93 Co 0.05 W 0.02 O 2 Or LiNi 0.97 Co 0.02 W 0.01 O 2 。
The doping element is one or more of B, ti, al, nb, sb, sn, si, sc, Y, ge and Zr;
the chemical composition of the lithium ion conductor layer is Li 3 BO 3 、Li 2 WO 4 、Li 2 MoO 4 、Li 2 TiO 3 、LiAlO 2 、LiNbO 3 、LiSbO 3 、Li 2 SnO 3 、Li 4 SiO 4 、Li 2 GeO 3 、Li 2 ZrO 3 、Li 3 PO 4 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 1.8 Sc 0.8 Ti 1.2 (PO 4 ) 3 And Li 1.4 Y 0.4 Ti 1.6 (PO 4 ) 3 One or more of them.
In the present invention, the molar ratio of the doping element to the metal element in the ternary positive electrode material matrix is preferably 0.01 to 1, more preferably 0.05 to 0.5.
In the present invention, the content of the lithium ion conductor layer in the bulk-doped ternary positive electrode material having a surface coated with a lithium ion conductor is preferably 0.1 to 10wt.%, more preferably 0.5 to 8wt.%, and even more preferably 1 to 5wt.%. In the present invention, the thickness of the lithium ion conductor layer is preferably 1 to 100nm, preferably 10 to 80nm, and more preferably 30 to 50nm.
In the present invention, the particle size of the bulk-doped ternary positive electrode material having a surface coated with a lithium ion conductor is preferably 1 to 15 μm, and more preferably 5 to 10 μm. In the invention, the tap density of the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor is preferably 2.0-3.0 gcm -3 The energy density is preferably 820 to 920 Wh/kg -1 。
The invention provides an application of the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor in a lithium ion power battery. The method of the present invention is not particularly limited, and the method may be applied according to a method known in the art.
The bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor, and the preparation method and application thereof provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Nickel sulfate and cobalt sulfate were mixed in a ratio of n (Ni) =0.9, n (Co) = 0.09 -1 The molybdenum trioxide is dissolved in 6.0wt.% sodium hydroxide solution to prepare 0.55L of the aqueous solution of molybdenum with the molar concentration of 0.182 mol.L -1 Preparing 9.0L of sodium hydroxide (precipitant) into 10.0% aqueous solution, and preparing 8.0L of ammonia water into 7.0 mol.L -1 Then the mixed salt solution, the alkali solution of the molybdenum element, the sodium hydroxide solution and the ammonia water solution are dripped into the coprecipitation reaction kettle in a parallel flow manner and are continuously stirred, and the dripping speed is 2 mL/min -1 The temperature of the reaction kettle is controlled to be 55 ℃, the stirring speed is 1200rpm, the pH value is not larger than 12.3, and the concentration of the complexing agent is 0.57 mol.L -1 Carrying out coprecipitation reaction for 50h to obtain nickel-cobalt-molybdenum hydroxide precursor slurry, aging for 2h, carrying out solid-liquid separation, repeatedly carrying out water suction filtration and washing on the obtained solid until the pH value of the filtrate is 9.5, filtering, and carrying out forced air drying at 100 ℃ for 16h to obtain a nickel-cobalt-molybdenum hydroxide precursor;
the prepared 10g of nickel-cobalt-molybdenum hydroxide precursor is dispersed in 30mL of ethanol, and the stirring speed is controlled at 500rpm. And dropwise adding an ethanol mixed solution dispersed with tetrabutyl titanate into the precursor suspension (the addition of Ti can be calculated according to the stoichiometric ratio and generally accounts for 2.0 percent of the total material molar ratio), continuously stirring for 3 hours, and heating the suspension to 80 ℃ to volatilize ethanol. Volatilizing ethanol to obtain nickel hydroxide cobalt molybdenum precursor powder with the surface coated with titanium hydroxide;
pre-oxidizing the nickel-cobalt-molybdenum hydroxide precursor with the surface coated with titanium hydroxide for 6 hours at the temperature of 400 ℃ to obtain the nickel-cobalt-molybdenum hydroxide precursorAnd (2) mixing lithium hydroxide and the nickel-cobalt-molybdenum oxide precursor coated with titanium oxide on the surface according to the molar ratio of the total amount of lithium to metal ions in the precursor of 1.07 2 TiO 3 ) The lithium nickel cobalt molybdate powder of (1).
Wherein, SEM image of nickel cobalt molybdenum oxide precursor coated with titanium oxide on surface is shown in figure 1; as can be seen from fig. 1, the titanium hydroxide coating layer is uniformly dense.
An SEM image of the lithium nickel cobalt molybdate positive electrode material doped with bulk titanium and coated with lithium metatitanate on the surface is shown in fig. 2. As can be seen from FIG. 2, the particle size of the primary particles of the cathode material is about 0.2 μm, part of the titanium element is successfully blended into the cathode material, part of the titanium element forms a lithium metatitanate coating layer on the surface of the spherical particles, no other impurity phase occurs, and the thickness of the coating layer is about 5nm.
An XRD spectrogram of the nickel-cobalt lithium molybdate anode material doped with bulk titanium and coated with lithium metatitanate on the surface is shown in figure 3. As can be seen from fig. 3, a part of the titanium element was successfully incorporated into the positive electrode material.
The tap density of the cathode material is detected according to GBT5162-2006, and is 2.6gcm -3 。
The obtained bulk titanium (Ti) is doped and the surface is coated with lithium metatitanate (Li) 2 TiO 3 ) The nickel-cobalt lithium molybdate anode material is an anode, the metal lithium is a cathode, and 1.2M LiPF 6 (EC: EMC =3 (Vol) 7, 2.0wt% of VC) as electrolyte, and assembling the electrolyte into a CR2025 button half cell by adopting Celgard2320 diaphragm, and performing performance test in a voltage interval of 2.7-4.3V.
The first charge-discharge curve chart of the obtained button cell under the conditions of 0.1C of current density and 2.7-4.3V of voltage is shown in figure 4, the multiplying power cycle performance curve chart is shown in figure 5, and the cycle curve chart is shown in figure 6.
As can be seen from FIGS. 4 to 6, the specific first discharge capacity of the positive electrode material was 220.6 at 30 ℃5mAhg -1 Corresponding to an energy density of about 820 Wh.kg -1 The first charge-discharge efficiency is 87.90%, the specific discharge capacity retention rate at 5.0C is 83.91%, and the specific discharge capacity retention rate at 1.0C after 100 charge/discharge cycles is 92.36%, which indicates that the bulk phase titanium (Ti) is doped and the surface of the bulk phase titanium metatitanate (Li) is coated 2 TiO 3 ) The ternary cathode material of nickel cobalt lithium molybdate has better multiplying power and cycle performance.
Example 2
Nickel sulfate and cobalt sulfate were mixed in a ratio of n (Ni) = 0.09 -1 Dissolving ammonium molybdate in 6.0wt.% sodium hydroxide solution to obtain 0.55L of aqueous solution containing molybdenum element with a molar concentration of 0.182 mol.L -1 Preparing 9.0L of sodium hydroxide (precipitant) into 10.0% aqueous solution, and preparing 8.0L of ammonia water into 7 mol.L -1 Then the mixed salt solution, the alkali solution of the molybdenum element, the sodium hydroxide solution and the ammonia solution are dripped into the coprecipitation reaction kettle in a parallel flow manner and are continuously stirred, and the dripping speed is 2 mL/min -1 The temperature of the reaction kettle is controlled to be 55 ℃, the stirring speed is 1200rpm, the pH value is 12.3, and the concentration of the complexing agent is 0.57 mol.L -1 Carrying out coprecipitation reaction for 50h to obtain nickel-cobalt-molybdenum hydroxide precursor slurry, aging for 2h, carrying out solid-liquid separation, repeatedly pumping, filtering and washing the obtained solid until the pH value of the filtrate is 9.5, filtering, and carrying out forced air drying at 100 ℃ for 16h to obtain a nickel-cobalt-molybdenum hydroxide precursor;
the prepared 10g of nickel-cobalt-molybdenum hydroxide precursor was dispersed in 30mL of propanol with the stirring speed controlled at 500rpm. And dropwise adding a propanol mixed solution dispersed with tetraethyl orthosilicate into the precursor suspension (the adding amount of Si accounts for 3.0 percent of the total material molar ratio), continuously stirring for 3 hours, and heating the suspension to 90 ℃ to volatilize propanol. Volatilizing propanol to obtain nickel hydroxide cobalt molybdenum precursor powder with the surface coated with silicon hydroxide;
pre-oxidizing the nickel-cobalt-molybdenum hydroxide precursor with the surface coated with the silicon hydroxide for 6 hours at 400 ℃ to obtain a nickel-cobalt-molybdenum oxide precursor with the surface coated with the silicon oxide, and mixing lithium hydroxide and nickel with the surface coated with the silicon oxideMixing a cobalt molybdenum oxide precursor according to the molar ratio of lithium to the total amount of metal ions in the precursor of 1.07 4 SiO 4 ) The lithium nickel cobalt molybdate powder of (1).
Wherein, the SEM image of the nickel-cobalt-molybdenum oxide precursor with the surface coated with the silicon oxide is shown in figure 7; as can be seen from fig. 7, the silicon hydroxide coating layer was uniformly dense.
Bulk silicon (Si) doped and surface coated with lithium silicate (Li) 4 SiO 4 ) The SEM image of the lithium nickel cobalt molybdate cathode material is shown in fig. 8. As can be seen from fig. 8, the primary particle size of the positive electrode material was about 0.3 μm, a lithium silicate coating layer was formed on the surface of the spherical particles by a part of silicon element, no other impurity phase was present, and the coating layer thickness was about 2nm.
Bulk silicon (Si) doped and surface coated with lithium silicate (Li) 4 SiO 4 ) The XRD spectrum of the nickel cobalt lithium molybdate cathode material is shown in figure 9. As can be seen from fig. 9, a part of the silicon element was successfully incorporated into the positive electrode material.
The tap density of the cathode material is detected according to GBT5162-2006, and is 2.5gcm -3 。
The obtained bulk silicon-doped lithium nickel cobalt molybdate positive electrode material with the surface coated with lithium silicate is assembled into a CR2025 button type half cell in the way of example 1, and performance test is carried out in a voltage interval of 2.7-4.3V.
The first charge-discharge curve chart of the obtained button cell under the conditions of 0.1C of current density and 2.7-4.3V of voltage is shown in figure 10, the multiplying power cycle performance curve chart is shown in figure 11, and the cycle curve chart is shown in figure 12.
As can be seen from FIGS. 11 to 12, the first discharge specific capacity of the positive electrode material was 226.56mAhg at 30 ℃ -1 The corresponding energy density is about 850 Wh.kg -1 The first charge-discharge efficiency is about 89.87%, the specific discharge capacity retention rate of 5.0C is 87.68%, and the specific discharge capacity retention rate of 77.78% after 100 times of 1.0C charge/discharge cycles, indicating bodyPhase silicon (Si) doped and surface coated with lithium silicate (Li) 4 SiO 4 ) The rate and cycle performance of the standard nickel-cobalt lithium molybdate ternary cathode material can be obviously improved through modification.
Example 3
Nickel sulfate and cobalt sulfate were mixed in a ratio of n (Ni) = 0.07 to prepare 5.0L of a mixture having a total metal ion concentration of 1.6mol · L -1 An aqueous solution of (a); sodium tungstate is dissolved in 5.0wt.% sodium hydroxide solution to prepare 0.5L of tungsten element with the molar concentration of 0.182 mol.L -1 Preparing 6.0L of aqueous solution with the mass concentration of 8.0wt.% by using potassium hydroxide and preparing 7.0L of ammonia water with the molar concentration of 6.5 mol.L -1 An aqueous solution of (a); dropwise adding the mixed salt solution, the alkali solution of the tungsten element, the sodium hydroxide solution and the ammonia water solution into the coprecipitation reaction kettle in a concurrent flow manner and continuously stirring, wherein the dropwise adding speed is 3 mL/min -1 The temperature of the reaction kettle is controlled to be 60 ℃, the stirring speed is 1000rpm, the pH is not less than 12.2, and the concentration of the complexing agent is 0.55 mol.L -1 After the reaction is carried out for 60 hours, obtaining nickel-cobalt-tungsten hydroxide precursor slurry, aging for 1 hour, carrying out solid-liquid separation, repeatedly carrying out suction filtration and water washing until the pH value of the filtrate is 9.3, filtering, and carrying out forced air drying at 90 ℃ for 18 hours to obtain a nickel-cobalt-tungsten hydroxide precursor;
20g of the prepared nickel-cobalt-tungsten hydroxide precursor was dispersed in 50mL of isopropanol, and the stirring speed was controlled at 600rpm. And dropwise adding an isopropanol mixed solution (the addition of Ti accounts for 1.0 percent of the total material molar ratio) dispersed with tetrabutyl titanate into the precursor suspension, continuously stirring for 2 hours, and heating the suspension to 95 ℃ to volatilize isopropanol. Volatilizing isopropanol to obtain nickel hydroxide, cobalt hydroxide and tungsten hydroxide precursor powder with titanium hydroxide coated on the surface;
pre-oxidizing the nickel-cobalt-tungsten hydroxide precursor with the surface coated with titanium hydroxide for 3h at 450 ℃ to obtain a nickel-cobalt-tungsten oxide precursor with the surface coated with titanium oxide, mixing lithium hydroxide with the nickel-cobalt-tungsten oxide precursor with the surface coated with titanium oxide according to the molar ratio of lithium to the total amount of metal ions in the precursor of 1.05(Ti) -doped and surface-coated lithium metatitanate (Li) 2 TiO 3 ) The nickel cobalt lithium tungstate powder.
Wherein, the SEM image of the nickel hydroxide cobalt tungsten precursor coated with titanium hydroxide on the surface is shown in FIG. 13; as can be seen from fig. 13, the titanium hydroxide coating layer was uniformly dense.
Bulk phase titanium (Ti) -doped and surface-coated lithium metatitanate (Li) 2 TiO 3 ) The SEM image of the lithium nickel cobalt tungstate positive electrode material is shown in fig. 14. As can be seen from fig. 14, the primary particle size of the positive electrode material is about 0.1 μm, a part of titanium elements form a lithium metatitanate coating layer on the surface of the spherical particles, no other impurity phase occurs, and the thickness of the coating layer is about 6nm.
Bulk phase titanium (Ti) -doped and surface-coated lithium metatitanate (Li) 2 TiO 3 ) The XRD spectrum of the lithium nickel cobalt tungstate cathode material is shown in figure 15. As can be seen from fig. 15, part of the titanium element was successfully incorporated into the positive electrode material.
Detecting the tap density of the cathode material according to GBT5162-2006, wherein the tap density is 2.3gcm -3 。
The obtained lithium nickel cobalt tungstate cathode material doped with bulk titanium and coated with lithium metatitanate on the surface is assembled into a CR2025 button half cell in the way of example 1, and a performance test is carried out in a voltage interval of 2.7-4.3V.
The first charge-discharge curve chart of the obtained button cell under the conditions of 0.1C of current density and 2.7-4.3V of voltage is shown in figure 16, the multiplying power cycle performance curve chart is shown in figure 17, and the cycle curve chart is shown in figure 18.
As can be seen from FIGS. 14 to 16, the first specific discharge capacity of the positive electrode material at 30 ℃ is 219.92mAhg -1 Corresponding to an energy density of 830 Wh.kg -1 The initial charge-discharge efficiency is 84.86%, the specific discharge capacity retention rate at 5.0C is about 87.65%, and the specific discharge capacity retention rate at 1.0C after 100 charge/discharge cycles is 103.23%, which indicates that the bulk phase titanium (Ti) doped and surface-coated lithium metatitanate (Li) is 2 TiO 3 ) The nickel cobalt lithium tungstate ternary cathode material has better multiplying power and cycle performance.
Comparative example 1
A nickel cobalt molybdenum hydroxide precursor was prepared in the manner of example 1;
pre-oxidizing the nickel-cobalt-molybdenum hydroxide precursor for 6h at 400 ℃ to obtain a nickel-cobalt-molybdenum oxide precursor, mixing lithium hydroxide and the nickel-cobalt-molybdenum oxide precursor according to a molar ratio of the total amount of lithium to metal ions in the precursor of 1.07.
Wherein, the SEM image of the nickel-cobalt-molybdenum hydroxide precursor is shown in figure 19; as can be seen from fig. 19, the precursor material secondary particles are formed by closely packing the flaky primary particles, and the surface of the precursor material secondary particles is free from other coatings.
An SEM image of the lithium nickel cobalt molybdate cathode material is shown in fig. 20. As can be seen from fig. 20, the primary particle size of the positive electrode material was about 0.2 μm.
The XRD spectrum of the lithium nickel cobalt molybdate cathode material is shown in figure 21. As can be seen from fig. 21, the positive electrode material had a layered structure, good crystallinity, and no other impurity peak.
Detecting the tap density of the cathode material according to GBT5162-2006, wherein the tap density is 2.4gcm -3 。
The obtained nickel-cobalt lithium molybdate cathode material is assembled into a CR2025 button type half cell in the mode of the embodiment 1, and the performance test is carried out in the voltage interval of 2.7-4.3V.
The first charge-discharge curve chart of the obtained button cell under the conditions of 0.1C of current density and 2.7-4.3V of voltage is shown in figure 22, the multiplying power cycle performance curve chart is shown in figure 23, and the cycle curve chart is shown in figure 24.
As can be seen from FIGS. 22 to 24, the first discharge capacity of the comparative positive electrode material was 216.29mAhg at 30 ℃ -1 Corresponding to an energy density of about 820 Wh.kg -1 The first charge-discharge efficiency was 88.15%, the 5.0C discharge capacity retention rate was 81.03%, and the discharge capacity retention rate after 100 cycles of 1.0C charge/discharge was 75.03%.
Comparative example 2
A nickel cobalt tungsten hydroxide precursor was prepared in the manner of example 3.
Pre-oxidizing the nickel-cobalt-tungsten hydroxide precursor for 3h at 450 ℃ to obtain a nickel-cobalt-tungsten oxide precursor, mixing lithium hydroxide and the nickel-cobalt-tungsten oxide precursor according to the molar ratio of the total amount of lithium to metal ions in the precursor of 1.05, carrying out ball milling and mixing for 50min by using 5mm polytetrafluoroethylene balls, wherein the ball milling rotation speed is 250rpm, sintering the mixture for 24h at 710 ℃, and crushing and grading sintered materials to obtain the nickel-cobalt-tungsten lithium powder.
Wherein, the SEM image of the nickel-cobalt-tungsten hydroxide precursor is shown in figure 25; as can be seen from fig. 25, the precursor material secondary particles are formed by closely packing the sheet-like primary particles, and the surface of the precursor material secondary particles is free from other coatings.
An SEM image of the lithium nickel cobalt tungstate positive electrode material is shown in fig. 26. As can be seen from fig. 26, the primary particle size of the positive electrode material was about 0.1 μm.
The XRD spectrum of the lithium nickel cobalt tungstate cathode material is shown in figure 27. As can be seen from fig. 27, this positive electrode material had a layered structure, good crystallinity, and no other impurity peak.
The tap density of the cathode material is detected according to GBT5162-2006, and is 2.3gcm -3 。
The obtained lithium nickel cobalt tungstate cathode material is assembled into a CR2025 button type half cell according to the mode of the embodiment 1, and the performance test is carried out within the voltage interval of 2.7-4.3V.
The first charge-discharge curve chart of the obtained button cell under the conditions of 0.1C of current density and 2.7-4.3V of voltage is shown in figure 28, the multiplying power cycle performance curve chart is shown in figure 29, and the cycle curve chart is shown in figure 30.
As can be seen from FIGS. 28 to 30, the first discharge capacity of the comparative positive electrode material was 216.98mAhg at 30 ℃ -1 Corresponding to an energy density of about 820 Wh.kg -1 The first charge-discharge efficiency was 87.95%, the 5.0C discharge capacity retention rate was 80.66%, and the discharge capacity retention rate after 100 cycles of 1.0C charge/discharge was 79.53%.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of a bulk phase doped ternary cathode material with a surface coated with a lithium ion conductor comprises the following steps:
mixing soluble nickel salt, soluble cobalt salt and water to obtain a mixed salt solution; the molar ratio of nickel ions to cobalt ions in the mixed salt solution is 0.9-1;
mixing the mixed salt solution, a VIB group metal source, a precipitator, a complexing agent and water, and carrying out coprecipitation reaction to obtain a hydroxide precursor, wherein the VIB group metal source is a molybdenum source or a tungsten source;
mixing the hydroxide precursor, soluble salt of the doping element and a solvent, and carrying out hydrolysis reaction to obtain a hydroxide precursor with the surface coated with a lithium ion conductor precursor; the doping element is one or more of B, ti, al, nb, sb, sn, si, ge and Zr; the solvent is water and/or alcohol;
heating and oxidizing the hydroxide precursor coated with the lithium ion conductor precursor on the surface to obtain an oxide precursor;
and mixing the oxide precursor with lithium salt, and sintering to obtain the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor.
2. The preparation method according to claim 1, wherein the precipitant is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate;
the complexing agent is one or more of ammonia water, disodium ethylene diamine tetraacetate, citric acid, sodium citrate, oxalic acid and sodium oxalate.
3. The process according to claim 1 or 2, characterized in that the molar ratio of the total metal ions in the mixed salt solution to the group VIB metal ions in the group VIB metal source is between 0.93 and 0.99;
the temperature of the precipitation reaction is 35-85 ℃, and the time is 5-80 h.
4. The method according to claim 1, wherein the molar ratio of the total metal ions to the ions of the doping element in the hydroxide precursor is 0.95 to 0.995.
5. The method according to claim 1 or 4, wherein the hydrolysis reaction is carried out at a temperature of 60 to 95 ℃ for 1 to 5 hours.
6. The preparation method according to claim 1, wherein the temperature of the heating oxidation is 400-600 ℃ and the time is 1-10 h.
7. The production method according to claim 1, wherein the molar ratio of total metal ions in the oxide precursor to lithium ions in the lithium salt is 1;
the sintering temperature is 600-820 ℃ and the sintering time is 10-20 h.
8. The bulk phase doping ternary cathode material with the surface coated with the lithium ion conductor, which is prepared by the preparation method of any one of claims 1 to 7, comprises the bulk phase doping ternary cathode material and a lithium ion conductor layer coated on the surface of the bulk phase doping ternary cathode material;
the bulk phase doped ternary cathode material comprises a ternary cathode material matrix and a doping element bulk phase doped in the ternary cathode material matrix, and the chemical composition of the ternary cathode material is LiNi x Co y Mo 1-x-y O 2 Or LiNi x Co y W 1-x- y O 2 Wherein x is more than or equal to 0.9<1.0，0.01≤y<0.1, and x + y<1；
The doping element is one or more of B, ti, al, nb, sb, sn, si, sc, Y, ge and Zr;
the chemical composition of the lithium ion conductor layer is Li 3 BO 3 、Li 2 WO 4 、Li 2 MoO 4 、Li 2 TiO 3 、LiAlO 2 、LiNbO 3 、LiSbO 3 、Li 2 SnO 3 、Li 4 SiO 4 、Li 2 GeO 3 、Li 2 ZrO 3 、Li 3 PO 4 、Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、Li 1.8 Sc 0.8 Ti 1.2 (PO 4 ) 3 And Li 1.4 Y 0.4 Ti 1.6 (PO 4 ) 3 One or more of them.
9. The bulk-doped ternary cathode material with the surface coated with the lithium ion conductor according to claim 8, wherein the molar ratio of the doping element to the metal element in the matrix of the ternary cathode material is 0.01 to 1;
the content of the lithium ion conductor layer in the bulk phase doped ternary cathode material with the surface coated with the lithium ion conductor is 0.1-10 wt.%.
10. The use of the bulk doped ternary positive electrode material with a surface coated with a lithium ion conductor according to claim 8 or 9 in a lithium ion power battery.
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