CN110034274B - Modified ternary cathode material, preparation method thereof and lithium ion battery - Google Patents

Modified ternary cathode material, preparation method thereof and lithium ion battery Download PDF

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CN110034274B
CN110034274B CN201810025769.7A CN201810025769A CN110034274B CN 110034274 B CN110034274 B CN 110034274B CN 201810025769 A CN201810025769 A CN 201810025769A CN 110034274 B CN110034274 B CN 110034274B
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cathode material
ternary cathode
ternary
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positive electrode
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CN110034274A (en
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周明炯
赵伟倩
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Ningbo Nanomicro Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
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Abstract

Compared with the prior art, the content of Al in the ternary cathode material particles of the modified ternary cathode material is gradually decreased from the outer surface to the inner part of the ternary cathode material particles, and the specific capacity and the cycle performance of the material are improved. The lithium ion battery prepared from the modified ternary cathode material has high specific capacity and excellent cycle performance. After the anode material precursor is obtained, the nano aluminum oxide is mixed with the anode material precursor and the lithium compound and sintered to obtain the ternary anode material particles. The method for adding aluminum is beneficial to improving the specific capacity and the cycle performance of the material. In addition, the lithium ion battery prepared finally has higher specific capacity and better cycle performance by further washing with a specific detergent after heat treatment.

Description

Modified ternary cathode material, preparation method thereof and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a modified ternary anode material, a preparation method thereof and a lithium ion battery.
Background
Lithium ion batteries are favored because of their high specific capacity and long service life, and they have advantages of small size, light weight, low self-discharge, no memory effect, etc., and thus are widely used. Currently, the anode materials adopted by lithium ion batteries mainly include lithium cobaltate, lithium manganate, lithium iron phosphate, ternary anode materials and the like. Among them, the ternary positive electrode material has a high specific capacity, good thermal stability and low price, and thus has been a research hotspot.
At present, the main synthesis method of the ternary cathode material is a ternary coprecipitation method, namely: and simultaneously adding cobalt salt, nickel salt, manganese salt and aluminum salt into the liquid-phase alkaline solution, coprecipitating to produce a nickel-cobalt-manganese-aluminum hydroxide precursor, and mixing and sintering the precursor and a lithium source to obtain the target cathode material. The ternary cathode material obtained by the method is easy to generate side reaction with electrolyte during the charge and discharge processes, so that the electrolyte is decomposed and the structure of the material collapses, and the electrochemical performance and the cycling stability of the material are seriously reduced. Meanwhile, the particle agglomeration of the ternary cathode material also influences the electrochemical performance and the cycle stability of the material.
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a modified ternary cathode material, a preparation method thereof, and a lithium ion battery, wherein the lithium ion battery prepared from the modified ternary cathode material has a high specific capacity and a good cycle performance.
The invention provides a modified ternary cathode material, which comprises the following components in parts by weight:
ternary positive electrode material particles and a protective layer coated on the outer surfaces of the ternary positive electrode material particles;
the ternary cathode material particles are composed of a ternary cathode material, and the general formula of the ternary cathode material is Li (NixCoyMnzAlv) O2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0; v is more than or equal to 0.1 and more than or equal to 0.01, and z + v is 0.1;
in the ternary cathode material particles, the content of Al is gradually decreased from the outer surface to the inner part of the ternary cathode material particles.
Preferably, the component of the protective layer is an oxide of a metal or a phosphate of a metal.
The invention also provides a preparation method of the modified ternary cathode material, which comprises the following steps:
A) mixing the precursor of the anode material, nano alumina and a lithium compound, and sintering to obtain ternary anode material particles;
the general formula of the positive electrode material precursor is NixCoy (OH) 2Or NixCoyMnz (OH)2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0;
B) mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain a ternary cathode material with a coating structure;
C) and carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
Preferably, the molar ratio of the positive electrode material precursor to the nano-alumina to the lithium compound is 0.9-1: 0.01-0.1: 1.0 to 1.07.
Preferably, the sintering temperature is 600-900 ℃, and the sintering time is 6-20 h.
Preferably, the metal compound comprises one or more of metal oxide, metal halide, metal phosphate, metal sulfate, metal nitrate, metal chloride and metal organic salt;
the metal compound accounts for 0.5-2 wt% of the ternary cathode material particles.
Preferably, the metal oxide is selected from Al2O3、ZnO、ZrO2、TiO2One or more of the above;
the metal halide is selected from AlCl3、ZrCl4、AlF3And SrBr2One or more of the above;
the metal phosphate is selected from AlPO4And/or YPO4；
The metal sulfate is selected from Al2(SO4)3、Zr(SO4)2And SrSO 4One or more of the above;
the metal nitrate is selected from Al (NO)3)3、Sr(NO3)2And Zr (NO)3)4One or more of the above;
the metal chloride is selected from AlCl3、YCl3And SrCl2One or more of the above;
the metal organic salt is selected from one or more of tetrabutyl titanate, aluminum isopropoxide and ethyl orthosilicate.
Preferably, the heat treatment temperature is 300-600 ℃, and the heat treatment time is 3-6 h.
Preferably, after the heat treatment, the method further comprises washing and tempering the heat-treated material;
the detergent adopted by washing comprises one or more of water, alcohol organic matters and surfactants;
the tempering temperature is 300-600 ℃; the tempering time is 2-8 h.
The invention also provides a lithium ion battery which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, and is characterized in that the positive electrode comprises the modified ternary positive electrode material or the modified ternary positive electrode material prepared by the preparation method.
The invention provides a modified ternary cathode material, which comprises the following components:
a modified ternary positive electrode material comprising:
ternary positive electrode material particles and a protective layer coated on the outer surfaces of the ternary positive electrode material particles;
The ternary cathode material particles are composed of a ternary cathode material, and the general formula of the ternary cathode material is Li (NixCoyMnzAlv) O2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0; v is more than or equal to 0.1 and more than or equal to 0.01, and z + v is 0.1;
in the ternary cathode material particles, the content of Al is gradually decreased from the outer surface to the inner part of the ternary cathode material particles.
Compared with the prior art, in the ternary cathode material particles of the modified ternary cathode material, the content of Al is gradually reduced from the outer surface to the inner part of the ternary cathode material particles, and the specific capacity and the cycle performance of the material are improved. The lithium ion battery prepared from the modified ternary cathode material has high specific capacity and excellent cycle performance.
The invention provides a preparation method of a modified ternary cathode material, which comprises the following steps:
A) mixing the precursor of the anode material, nano alumina and a lithium compound, and sintering to obtain ternary anode material particles;
the general formula of the positive electrode material precursor is NixCoy (OH)2Or NixCoyMnz (OH)2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0;
B) mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain a ternary cathode material with a coating structure;
C) And carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
After obtaining the precursor of the anode material, the invention mixes the nano alumina with the precursor of the anode material and the lithium compound, and then carries out sintering to obtain the ternary anode material particles. The aluminum adding method can enable part of aluminum oxide to enter the crystal lattice of the ternary cathode material to realize aluminum doping through sintering, and the content of Al in the obtained ternary cathode material particles is gradually reduced from the outer surface to the inner part of the ternary cathode material particles, so that the specific capacity and the cycle performance of the material are improved. In addition, the specific detergent is further washed after the heat treatment, so that the influence of valence change of nickel element in the ternary positive electrode material on the electrochemical performance of the material due to the conventional water washing of the ternary positive electrode material is avoided, and finally, the lithium ion battery prepared from the modified ternary positive electrode material has high specific capacity and excellent cycle performance.
Experimental results show that the first charge-discharge specific capacity of the lithium ion battery prepared by the modified ternary cathode material is not lower than 180mAh/g under the conditions that the charge-discharge voltage is 3.0-4.3V and the charge-discharge current density is 200 mA/g; after the charge and the discharge are carried out for 100 times in a circulating manner, the discharge specific capacity is not lower than 170mAh/g, the capacity retention rate is not lower than 90%, and the cycle performance is better.
Drawings
Fig. 1 is an SEM image of ternary cathode material particles prepared in example 1 of the present invention;
FIG. 2 is an SEM image of a modified ternary cathode material prepared in example 1 of the invention;
FIG. 3 is a graph of cycle performance of the modified ternary cathode material prepared in example 1 of the present invention;
fig. 4 is a rate performance graph of the modified ternary cathode material prepared in example 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below with reference to embodiments of the present invention, and it should be apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The invention provides a modified ternary cathode material, which comprises the following components in parts by weight:
ternary positive electrode material particles and a protective layer coated on the outer surfaces of the ternary positive electrode material particles;
the ternary cathode material particles are composed of a ternary cathode material, and the general formula of the ternary cathode material is Li (NixCoyMnzAlv) O2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0; v is more than or equal to 0.1 and more than or equal to 0.01, and z + v is 0.1;
In the ternary cathode material particles, the content of Al is gradually decreased from the outer surface to the inner part of the ternary cathode material particles.
In the present invention, the ternary cathode material particles are formed by densely packing primary particles into secondary particles. The primary particles are spherical, and the particle size of the primary particles is preferably 200-300 nm. The particle size of the secondary particles is preferably 13-15 μm.
The component of the protective layer is preferably an oxide of a metal or a phosphate of a metal. The oxide of the metal is preferably one or more of aluminum oxide, zirconium oxide, strontium oxide and titanium oxide. The phosphate of the metal is preferably one or more of yttrium phosphate and aluminum phosphate. The thickness of the electrochemical inert material layer is preferably 1-10 nm.
The modified ternary cathode material provided by the invention is of a core-shell structure and comprises a core and a shell coated on the outer surface of the core. The inner core is made of a ternary anode material, and the outer shell is a protective layer.
The general formula of the ternary cathode material is Li (NixCoyMnzAlv) O2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0; v is more than or equal to 0.1 and more than or equal to 0.01, and z + v is more than or equal to 0.1.
In the inner core, the content of Al gradually decreases from the outer surface to the inner part of the inner core.
Compared with the prior art, in the ternary cathode material particles of the modified ternary cathode material, the content of Al is gradually reduced from the outer surface to the inner part of the ternary cathode material particles, and the specific capacity and the cycle performance of the material are improved. The lithium ion battery prepared from the modified ternary cathode material has high specific capacity and excellent cycle performance.
The invention provides a preparation method of a modified ternary cathode material, which comprises the following steps:
A) mixing the precursor of the anode material, nano alumina and a lithium compound, and sintering to obtain ternary anode material particles;
the general formula of the positive electrode material precursor is NixCoy (OH)2Or NixCoyMnz (OH)2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0;
B) mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain a ternary cathode material with a coating structure;
C) and carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
The invention firstly mixes the precursor of the anode material, the nano alumina and the lithium compound, and obtains the ternary anode material particles after sintering. After the anode material precursor is obtained, the nano aluminum oxide is mixed with the anode material precursor and the lithium compound and sintered to obtain the ternary anode material particles. The aluminum adding method can enable part of aluminum oxide to enter the crystal lattice of the ternary cathode material to realize aluminum doping through sintering, and the content of Al in the obtained ternary cathode material particles is gradually reduced from the outer surface to the inner part of the ternary cathode material particles, so that the specific capacity and the cycle performance of the material are improved. In addition, the specific detergent is further washed after the heat treatment, so that the phenomenon that the valence state of nickel element in the ternary positive electrode material is changed to influence the electrochemical performance of the material due to the conventional washing of the ternary positive electrode material is avoided, and finally, the lithium ion battery prepared from the modified ternary positive electrode material has high specific capacity and excellent cycle performance.
The general formula of the positive electrode material precursor is NixCoy (OH)2Or NixCoyMnz (OH)2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0;
in certain embodiments of the present invention, the positive electrode material precursor is Ni0.8Co0.15(OH)2、Ni0.6Co0.2Mn0.15(OH)2Or Ni0.8Co0.05Mn0.1(OH)2. The source of the precursor of the positive electrode material is not particularly limited, and the precursor can be self-made or generally sold in the market. The invention is preferably prepared according to the following method:
nickel sulfate, cobalt sulfate and manganese sulfate are mixed according to a molar ratio of 0.6-1.0: 0.05-0.2: 0-0.15 of the precursor is dissolved in deionized water, and a precursor of the anode material is obtained through a coprecipitation reaction.
The invention has no special limitation on the dosage of the deionized water, and can completely dissolve nickel sulfate, cobalt sulfate and manganese sulfate.
In the invention, the temperature of the coprecipitation reaction is preferably 40-60 ℃, the time of the coprecipitation reaction is preferably 72-120 h, and the pH value of the coprecipitation reaction is preferably 10-12. The coprecipitation is preferably carried out with stirring. The stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used. The stirring speed is preferably 400-850 r/min.
The lithium compound is preferably one or more of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, lithium sulfate and lithium chloride.
In the invention, the molar ratio of the positive electrode material precursor to the nano-alumina to the lithium compound is preferably 0.9-1: 0.01-0.1: 1.0 to 1.07. In certain embodiments of the present invention, the molar ratio of the positive electrode material precursor, nano alumina, and lithium compound is 1: 0.05: 1.05, 0.99: 0.05: 1.06, 1.0: 0.06: 1.04 or 0.99: 0.06: 1.06.
the sintering temperature is preferably 600-900 ℃. In certain embodiments of the invention, the temperature of the sintering is 750 ℃ or 900 ℃. The sintering time is preferably 6-20 h. In certain embodiments of the invention, the sintering time is 10 hours or 12 hours.
Obtaining ternary positive electrode material particles after sintering, wherein the general formula of the ternary positive electrode material in the ternary positive electrode material particles is preferably Li (NixCoyMnzAlv) O2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0; v is more than or equal to 0.1 and more than or equal to 0.01, and z + v is more than or equal to 0.1.
In certain embodiments of the invention, the ternary positive electrode material is LiNi0.8Co0.15Al0.05O2、LiNi0.6Co0.2Mn0.15Al0.05O2Or LiNi0.8Co0.05Mn0.1Al0.05O2。
After the ternary cathode material particles are obtained, mixing a metal compound with a solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain the ternary cathode material with a coating structure.
In the present invention, the solution of the ternary cathode material particles is preferably prepared according to the following method:
and dispersing the ternary cathode material particles in a solvent, and uniformly stirring to obtain a solution of the ternary cathode material particles.
The solvent is preferably one or more of deionized water and alcohol compounds. The alcohol compound is preferably ethanol and/or propanol.
The mass ratio of the ternary cathode material to the solvent is preferably 0.5-2: 1. in certain embodiments of the present invention, the solvent of the ternary cathode material is present in a mass ratio of 2: 1. 0.5: 1 or 1: 1.
the metal compound preferably comprises one or more of metal oxide, metal halide, metal phosphate, metal sulfate, metal nitrate, metal chloride and metal organic salt. Wherein the metal oxide is preferably Al2O3、ZnO、ZrO2、TiO2One or more of them. The metal halide is preferably AlCl3、ZrCl4、AlF3And SrBr2One or more of them. The metal phosphate is preferably AlPO4And/or YPO4. The metal sulfate is preferably Al2(SO4)3、Zr(SO4)2And SrSO4One or more of them. The metal nitrate is preferably Al (NO)3)3、Sr(NO3)2And Zr (NO)3)4One or more of them. The metal chloride salt is preferably AlCl 3、YCl3And SrCl2One or more of them. The metal organic salt is preferably one or more of tetrabutyl titanate, aluminum isopropoxide and ethyl orthosilicate.
In the present invention, the metal compound preferably accounts for 0.5 to 2 wt% of the ternary cathode material particles. In certain embodiments of the present invention, the metal compound comprises 0.5 wt%, 1 wt%, or 2 wt% of the ternary cathode material particles.
The mixing of the metal compound and the solution of the ternary cathode material particles is preferably: adding a metal compound to the solution of the ternary positive electrode material particles.
And mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain the ternary cathode material with the coating structure.
The pH value of the reaction is 7-13. In certain embodiments of the invention, the pH of the reaction is 11.5 or 11. The reagent for adjusting the pH of the reaction is preferably ammonia or an ammonium salt. The ammonium salt is preferably ammonium hydrogen phosphate. And when the reagent for adjusting the pH value of the reaction is ammonia water, the obtained ternary cathode material with the coating structure is a ternary cathode material with an outer layer uniformly coated with metal hydroxide. And when the reagent for adjusting the pH value of the reaction is ammonium salt, the obtained ternary cathode material with the coating structure is a ternary cathode material with an outer layer uniformly coated with metal phosphate.
The reaction is preferably carried out at room temperature. The reaction time is preferably 1-3 h. In certain embodiments of the invention, the reaction time is 1.5h or 2 h. The reaction is preferably carried out with stirring. The stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used. The stirring speed is preferably 100-300 r/min. In certain embodiments of the invention, the stirring speed is 150 r/min.
After the reaction, it is preferable to further include: and filtering, washing and drying the product after the reaction. The method of filtration is not particularly limited in the present invention, and a filtration method known to those skilled in the art may be used. The reagent used for the washing is preferably deionized water. The washing method of the present invention is not particularly limited, and a washing method known to those skilled in the art may be used. The drying temperature is preferably 80-130 ℃. In certain embodiments of the invention, the temperature of the drying is 120 ℃ or 125 ℃. The drying time is preferably 3-6 h. In certain embodiments of the invention, the drying time is 4h, 5h, or 6 h. The drying means is preferably a forced air drying cabinet.
And after obtaining the ternary cathode material with the coating structure, carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
The temperature of the heat treatment is preferably 300-600 ℃. In certain embodiments of the invention, the temperature of the heat treatment is 400 ℃ or 500 ℃. The time of the heat treatment is preferably 3-6 h. In certain embodiments of the present invention, the heat treatment time is 6 hours. The heat treatment is preferably carried out in a muffle furnace.
After the ternary cathode material coated with the metal hydroxide on the outer layer is subjected to the heat treatment, the obtained modified ternary cathode material is the ternary cathode material coated with the metal oxide on the outer layer. After the ternary cathode material coated with the metal phosphate on the outer layer is subjected to the heat treatment, the obtained modified ternary cathode material is the ternary cathode material coated with the metal phosphate on the outer layer.
After the heat treatment, washing and tempering the heat-treated material are preferably carried out, so as to obtain the modified ternary cathode material.
The washing is preferably carried out according to the following method:
and dispersing the heat-treated material in a detergent, and washing under stirring.
The detergent preferably comprises one or more of water, alcohol organic matters and surfactants. The alcohol organic matter is preferably one or more of ethanol, propanol and glycol. The surfactant is preferably one or more of polyvinyl alcohol, polyvinylpyrrolidone and polyethylene glycol.
The mass ratio of the heat-treated material to the detergent is preferably 0.1-10: 1. in certain embodiments of the present invention, the mass ratio of the heat-treated material to the detergent is 0.1: 1. 5: 1 or 10: 1.
the method of stirring is not particularly limited in the present invention, and a method of stirring known to those skilled in the art may be used. The stirring speed is preferably 100-300 r/min. In certain embodiments of the invention, the stirring speed is 150 r/min. The stirring time is preferably 0.5-2 h. In certain embodiments of the invention, the stirring time is 1 hour.
According to the invention, after heat treatment, washing with a specific detergent is carried out, in the prior art, after heat treatment, washing with water is required, and the valence state of nickel element in the ternary cathode material is changed due to washing with water, so that the electrochemical performance of the material is poor. According to the invention, through further washing with the specific detergent after the heat treatment, the situation that the valence state of nickel element in the ternary anode material is changed to influence the electrochemical performance of the material due to conventional water washing is avoided, and finally, the lithium ion battery prepared from the modified ternary anode material has high specific capacity and excellent cycle performance.
After washing, preferably drying and then tempering are carried out, thus obtaining the modified ternary cathode material. The drying temperature is preferably 80-130 ℃. In certain embodiments of the invention, the temperature of the drying is 120 ℃. The drying time is preferably 3-6 h. In certain embodiments of the invention, the drying time is 4h, 5h or 6 h. The drying device is preferably a forced air drying cabinet.
The tempering temperature is preferably 300-600 ℃. In certain embodiments of the invention, the tempering temperature is 400 ℃. The tempering time is preferably 2-8 h. In certain embodiments of the present invention, the tempering treatment time is 6 hours. The tempering treatment is preferably carried out in a muffle furnace.
After the tempering treatment, the method preferably further comprises: cooling and grinding. The temperature of the cooling is preferably room temperature. The method of polishing is not particularly limited in the present invention, and polishing methods known to those skilled in the art may be used.
The source of the raw material components used in the present invention is not particularly limited, and may be generally commercially available.
The invention also provides a lithium ion battery which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, and is characterized in that the positive electrode comprises the modified ternary positive electrode material or the modified ternary positive electrode material prepared by the preparation method.
The invention has no special limit to the types of the negative electrode, the diaphragm and the electrolyte, and the negative electrode can adopt a lithium sheet; the diaphragm can adopt a polypropylene microporous membrane; the electrolyte can adopt LiPF6Mixed solution of EC and DMC. Specifically, the modified ternary cathode material, the conductive carbon black Super-P and the binder (polyvinylidene fluoride) are mixed according to the weight ratio of 80: 10: 10, adding a proper amount of additive N-methyl pyrrolidone (NMP), then uniformly coating the mixture on an aluminum foil current collector, carrying out vacuum drying and rolling to prepare a positive plate, wherein a lithium plate is used as a negative plate, and LiPF is adopted6EC and DMC (1: 1, v/v) are prepared into 1mol/L mixed solution as electrolyte, and a polypropylene microporous membrane is selected as a diaphragm to assemble the R2032 type button cell.
The obtained simulated battery is subjected to a constant-current charging and discharging experiment, the cycle performance of the lithium ion battery is tested, the charging and discharging voltage is limited to 3.0-4.3V, and the charging and discharging current density is 200 mA/g. The electrochemical performance of the cell was tested using a Land tester (blue electronic, Inc., Wuhan City) at room temperature. Experimental results show that the first charge-discharge specific capacity of the lithium ion battery provided by the invention is not lower than 180 mAh/g; after the charge and the discharge are carried out for 100 times in a circulating manner, the discharge specific capacity is not lower than 170mAh/g, the capacity retention rate is not lower than 90%, and the cycle performance is better.
The invention provides a modified ternary cathode material, which comprises the following components in parts by weight:
ternary positive electrode material particles and a protective layer coated on the outer surfaces of the ternary positive electrode material particles;
the general formula of the ternary cathode material is Li (NixCoyMnzAlv) O2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0; v is more than or equal to 0.1 and more than or equal to 0.01, and z + v is 0.1;
in the ternary cathode material particles, the content of Al is gradually decreased from the outer surface to the inner part of the ternary cathode material particles.
Compared with the prior art, in the ternary cathode material particles of the modified ternary cathode material, the content of Al is gradually reduced from the outer surface to the inner part of the ternary cathode material particles, and the specific capacity and the cycle performance of the material are improved. The lithium ion battery prepared from the modified ternary cathode material has high specific capacity and excellent cycle performance.
The invention provides a preparation method of a modified ternary cathode material, which comprises the following steps:
A) mixing the precursor of the anode material, nano aluminum oxide and lithium salt, and sintering to obtain ternary anode material particles;
the general formula of the positive electrode material precursor is NixCoy (OH)2Or NixCoyMnz (OH)2；
Wherein x is more than or equal to 1 and more than or equal to 0.6, y is more than or equal to 0.1 and more than or equal to 0.05, and z is more than or equal to 0.1 and more than or equal to 0;
B) Mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain a ternary cathode material with a coating structure;
C) and carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
After obtaining the precursor of the anode material, the invention mixes the nano-alumina with the precursor of the anode material and lithium salt, and then carries out sintering to obtain the ternary anode material particles. The aluminum adding method can enable part of aluminum oxide to enter the crystal lattice of the ternary cathode material to realize aluminum doping through sintering, and the content of Al in the obtained ternary cathode material particles is gradually reduced from the outer surface to the inner part of the ternary cathode material particles, so that the specific capacity and the cycle performance of the material are improved. In addition, the specific detergent is further washed after the heat treatment, so that the influence of valence change of nickel element in the ternary positive electrode material on the electrochemical performance of the material due to the conventional water washing of the ternary positive electrode material is avoided, and finally, the lithium ion battery prepared from the modified ternary positive electrode material has high specific capacity and excellent cycle performance.
Experimental results show that the first charge-discharge specific capacity of the lithium ion battery prepared by the modified ternary cathode material is not lower than 180mAh/g under the conditions that the charge-discharge voltage is 3.0-4.3V and the charge-discharge current density is 200 mA/g; after the charge and the discharge are carried out for 100 times in a circulating manner, the discharge specific capacity is not lower than 170mAh/g, the capacity retention rate is not lower than 90%, and the cycle performance is better.
In order to further illustrate the present invention, the following examples are provided to describe in detail a modified ternary cathode material, a preparation method thereof and a lithium ion battery provided by the present invention, but should not be construed as limiting the scope of the present invention.
Example 1
Nickel sulfate and cobalt sulfate are mixed according to a molar ratio of 0.81: 0.15 is dissolved in deionized water, and the coprecipitation reaction is carried out for 100 hours at the temperature of 45 ℃ under the conditions that the stirring speed is 500r/min and the pH value is 10.5, thus obtaining the precursor Ni of the anode material0.8Co0.15(OH)2。
Precursor Ni of positive electrode material0.8Co0.15(OH)2The molar ratio of the nano aluminum oxide to the lithium hydroxide is 1: 0.05: 1.05, and sintering at 750 ℃ for 10 hours to obtainTernary positive electrode material particle LiNi0.8Co0.15Al0.05O2。
10g of ternary positive electrode material particles LiNi0.8Co0.15Al0.05O2Dispersing in 5g of mixed solvent consisting of deionized water and ethanol, and uniformly stirring to obtain a mixed solution. Subjecting YPO to 4Adding into the mixed solution, the YPO4Accounting for 0.5 wt% of the ternary cathode material, and stirring and reacting for 2h at room temperature. Stirring speed of the stirring reaction is 150r/min, and ammonia water is dripped to adjust pH of the stirring reaction to be 11, so that the ternary cathode material with the yttrium-coated hydroxide uniformly on the outer layer is obtained. Then, the ternary cathode material of which the outer layer is uniformly coated with yttrium hydroxide is filtered, washed by deionized water and dried for 5 hours in a forced air drying oven at 125 ℃. And then, carrying out heat treatment for 6h in a muffle furnace at 500 ℃ to obtain the ternary cathode material with the uniform outer layer coated with the yttrium oxide.
Uniformly coating the ternary cathode material with yttrium oxide on the outer layer according to the mass ratio of 0.1: 1 is dispersed in ethanol and washed with stirring. The stirring speed is 150r/min, and the stirring time is 1 h. After the washing was completed, the washed material was placed in a forced air drying cabinet and dried at 120 ℃ for 6 hours. Then, the steel was tempered in a muffle furnace at 400 ℃ for 6 hours. And cooling to room temperature, taking out, and grinding to obtain the modified ternary cathode material.
Scanning electron microscope scanning analysis is performed on the obtained ternary cathode material particles, and the result is shown in fig. 1, fig. 1 is an SEM image of the ternary cathode material particles prepared in example 1 of the present invention, and as can be seen from fig. 1, the ternary cathode material particles are spherical, the primary particles of the particles are about 200 to 300nm, and the primary particles are tightly packed into secondary particles, and the size of the secondary particles is about 13 to 15 μm.
Scanning electron microscope scanning analysis is performed on the obtained modified ternary cathode material, the result is shown in fig. 2, fig. 2 is an SEM image of the modified ternary cathode material prepared in embodiment 1 of the present invention, and it can be seen from fig. 2 that compared with ternary cathode material particles, the surface of the obtained modified ternary cathode material has a layer of coating film.
Mixing the modified ternary positive electrode material, conductive carbon black Super-P and a binder (polyvinylidene fluoride) according to a ratio of 80: 10: 10, adding a proper amount of additive N-methyl pyrrolidone (NMP), then uniformly coating the mixture on an aluminum foil current collector, carrying out vacuum drying and rolling to prepare a positive plate, wherein a lithium plate is used as a negative plate, and LiPF is adopted6EC and DMC (1:1, v/v) are prepared into 1mol/L mixed solution as electrolyte, and a polypropylene microporous membrane is selected as a diaphragm to assemble the R2032 type button cell.
And carrying out a constant-current charge and discharge experiment on the obtained simulated battery, testing the cycle performance of the lithium ion battery, limiting the charge and discharge voltage to be 3.0-4.3V, and controlling the charge and discharge current density to be 200 mA/g. The electrochemical performance of the cell was tested using a Land tester (blue electronic, Inc., Wuhan City) at room temperature. The cycle performance curve was obtained as shown in fig. 3. Fig. 3 is a cycle performance graph of the modified ternary cathode material prepared in example 1 of the present invention. As can be seen from fig. 3, the first discharge specific capacity of the lithium ion battery provided in this embodiment is 196mAh/g, the discharge specific capacity after 100 times of cyclic charge and discharge is 187mAh/g, the capacity retention rate is 95.4%, and the lithium ion battery has a better cycle performance.
Meanwhile, the charge-discharge cycle performance of the obtained lithium ion battery under different multiplying powers is also examined, as shown in fig. 4. Fig. 4 is a rate performance curve diagram of the modified ternary cathode material prepared in example 1 of the present invention, and it can be seen from fig. 4 that the specific discharge capacities of the lithium ion battery at 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C are 192 mAh/g, 185 mAh/g, 180 mAh/g, 173 mAh/g, 167 mAh/g, and 152mAh/g, respectively, and the rate performance is good.
Example 2
Nickel sulfate, cobalt sulfate and manganese sulfate are added according to a molar ratio of 0.61: 0.2: 0.15 is dissolved in deionized water, and the mixture is subjected to coprecipitation reaction for 110 hours at 50 ℃ under the conditions that the stirring speed is 550r/min and the pH value is 11, so as to obtain a precursor Ni of the anode material0.6Co0.2Mn0.15(OH)2。
Precursor Ni of positive electrode material0.6Co0.2Mn0.15(OH)2Nano alumina and lithium carbonateAccording to the molar ratio of 0.99: 0.05: 1.06, and sintering at 900 ℃ for 12h to obtain ternary cathode material particles LiNi0.6Co0.2Mn0.15Al0.05O2。
10g of ternary cathode material particles LiNi0.6Co0.2Mn0.15Al0.05O2Dispersed in 20g of deionized water, and stirred uniformly to obtain a mixed solution. Mixing AlCl3Adding into the mixed solution, and adding the AlCl3Accounting for 2 wt% of the ternary cathode material, and reacting for 2h at room temperature with stirring. Stirring speed of the stirring reaction is 150r/min, ammonia water is dripped to adjust pH of the stirring reaction to be 11.5, and the ternary cathode material with the outer layer uniformly coated with aluminum hydroxide is obtained. Then, the ternary cathode material with the outer layer uniformly coated with aluminum hydroxide was filtered, washed with deionized water, and dried in a forced air drying oven at 120 ℃ for 6 hours. And then, carrying out heat treatment for 6h in a muffle furnace at 400 ℃ to obtain the ternary cathode material with the outer layer uniformly coated with the alumina.
And uniformly coating the outer layer with the ternary cathode material of alumina according to the mass ratio of 10: 1 is dispersed in a mixed solution of deionized water and ethanol, and washed under stirring. The stirring speed is 150r/min, and the stirring time is 1 h. After the washing was completed, the washed material was placed in a forced air drying oven and dried at 120 ℃ for 6 hours. Then, the steel was tempered in a muffle furnace at 400 ℃ for 6 hours. And cooling to room temperature, taking out, and grinding to obtain the modified ternary cathode material.
Mixing the modified ternary positive electrode material, conductive carbon black Super-P and a binder (polyvinylidene fluoride) according to the weight ratio of 80: 10: 10, adding a proper amount of additive N-methyl pyrrolidone (NMP), then uniformly coating on an aluminum foil current collector, carrying out vacuum drying and rolling to prepare a positive plate, and adopting a lithium plate as a negative plate and LiPF6EC and DMC (1:1, v/v) are prepared into 1mol/L mixed solution as electrolyte, and a polypropylene microporous membrane is selected as a diaphragm to assemble the R2032 type button cell.
And carrying out a constant-current charge and discharge experiment on the obtained simulated battery, and testing the cycle performance of the lithium ion battery, wherein the charge and discharge voltage is limited to 3.0-4.3V, and the charge and discharge current density is 200 mA/g. The electrochemical performance of the battery is tested by using a Land tester (blue electronic corporation, Wuhan City), and the test condition is room temperature, so that the lithium ion battery provided by the embodiment has the specific discharge capacity of 181mAh/g for the first time, 170mAh/g for 100 times of cyclic charge and discharge, 93.9% of capacity retention rate, and better cyclic performance.
Example 3
Nickel sulfate, cobalt sulfate and manganese sulfate are mixed according to a molar ratio of 0.81: 0.05: 0.11 is dissolved in deionized water, and the mixture is subjected to coprecipitation reaction for 115 hours at 55 ℃ under the conditions that the stirring speed is 600r/min and the pH value is 11.5, so as to obtain a precursor Ni of the anode material0.8Co0.05Mn0.1(OH)2。
Precursor Ni of positive electrode material0.8Co0.05Mn0.1(OH)2The molar ratio of the nano aluminum oxide to the lithium hydroxide is 1.0: 0.06: 1.04 and sintering at 750 ℃ for 10h to obtain ternary cathode material particles LiNi0.8Co0.05Mn0.1Al0.05O2。
10g of ternary cathode material particles LiNi0.8Co0.05Mn0.1Al0.05O2Dispersing in 10g of mixed solvent consisting of deionized water and ethanol, and stirring uniformly to obtain mixed solution. ZrCl4Adding the ZrCl into the mixed solution4Accounting for 1 wt% of the ternary cathode material, and stirring and reacting for 1.5h at room temperature. Stirring speed of the stirring reaction is 150r/min, ammonia water is dripped to adjust pH of the stirring reaction to be 11.5, and the ternary cathode material with the outer layer uniformly coated with the hydroxide of zirconium is obtained. Then, the ternary positive electrode material of which the outer layer was uniformly coated with zirconium hydroxide was filtered, washed with deionized water, and dried in a forced air drying oven at 120 ℃ for 5 hours. And then, carrying out heat treatment for 6h in a muffle furnace at 400 ℃ to obtain the ternary cathode material with the outer layer uniformly coated with the zirconia.
Uniformly coating the outer layer with a zirconium oxide ternary cathode material according to the mass ratio of (5): 1, dispersing in a mixed solution of deionized water and ethanol, and washing under stirring. The stirring speed is 150r/min, and the stirring time is 1 h. After the washing was completed, the washed material was placed in a forced air drying cabinet and dried at 120 ℃ for 5 hours. Then, the steel was tempered in a muffle furnace at 400 ℃ for 6 hours. And cooling to room temperature, taking out, and grinding to obtain the modified ternary cathode material.
Mixing the modified ternary positive electrode material, conductive carbon black Super-P and a binder (polyvinylidene fluoride) according to a ratio of 80: 10: 10, adding a proper amount of additive N-methyl pyrrolidone (NMP), then uniformly coating the mixture on an aluminum foil current collector, carrying out vacuum drying and rolling to prepare a positive plate, wherein a lithium plate is used as a negative plate, and LiPF is adopted6EC and DMC (1:1, v/v) are prepared into 1mol/L mixed solution as electrolyte, and a polypropylene microporous membrane is selected as a diaphragm to assemble the R2032 type button cell.
And carrying out a constant-current charge and discharge experiment on the obtained simulated battery, testing the cycle performance of the lithium ion battery, limiting the charge and discharge voltage to be 3.0-4.3V, and controlling the charge and discharge current density to be 200 mA/g. The electrochemical performance of the battery is tested by using a Land tester (blue electronic corporation, Wuhan City), and the test condition is room temperature, so that the lithium ion battery provided by the embodiment has the specific discharge capacity of 189mAh/g for the first time, 179mAh/g for 100 times of cyclic charge and discharge, the capacity retention rate of 94.7%, and better cyclic performance.
Example 4
Nickel sulfate, cobalt sulfate and manganese sulfate are mixed according to a molar ratio of 0.81: 0.06: 0.1 is dissolved in deionized water, and the mixture is subjected to coprecipitation reaction for 90 hours at 50 ℃ under the conditions that the stirring speed is 650r/min and the pH value is 12, so as to obtain a precursor Ni of the anode material0.8Co0.05Mn0.1(OH)2。
Precursor Ni of positive electrode material0.8Co0.05Mn0.1(OH)2The molar ratio of the nano aluminum oxide to the lithium carbonate is 0.99: 0.06: 1.06, and sintering at 900 ℃ for 12h to obtain the ternary cathode material particle LiNi0.8Co0.05Mn0.1Al0.05O2。
10g of three elementsPositive electrode material particle LiNi0.8Co0.05Mn0.1Al0.05O2Dispersing in 10g of mixed solvent consisting of deionized water and ethanol, and uniformly stirring to obtain a mixed solution. Mixing Al2(SO4)3Adding the Al into the mixed solution2(SO4)3Accounting for 1 wt% of the ternary cathode material, and stirring and reacting for 1.5h at room temperature. And the stirring speed of the stirring reaction is 150r/min, and the pH value of the stirring reaction is adjusted to 9 by dropwise adding ammonium hydrogen phosphate to obtain the ternary cathode material with an outer layer uniformly coated with aluminum phosphate. Then, the ternary cathode material with the outer layer uniformly coated with aluminum phosphate was filtered, washed with deionized water, and dried in a forced air drying oven at 120 ℃ for 4 hours. And then, carrying out heat treatment for 6h in a muffle furnace at 400 ℃ to obtain the ternary cathode material with the outer layer uniformly coated with aluminum phosphate.
And uniformly coating the ternary cathode material with the outer layer coated with aluminum phosphate according to the mass ratio of (5): 1, dispersing in a mixed solution of deionized water and ethanol, and washing under stirring. The stirring speed is 150r/min, and the stirring time is 1 h. After the washing was completed, the washed material was placed in a forced air drying oven and dried at 120 ℃ for 4 hours. Then, the steel was tempered in a muffle furnace at 400 ℃ for 6 hours. And cooling to room temperature, taking out, and grinding to obtain the modified ternary cathode material.
Mixing the modified ternary positive electrode material, conductive carbon black Super-P and a binder (polyvinylidene fluoride) according to a ratio of 80: 10: 10, adding a proper amount of additive N-methyl pyrrolidone (NMP), then uniformly coating the mixture on an aluminum foil current collector, carrying out vacuum drying and rolling to prepare a positive plate, wherein a lithium plate is used as a negative plate, and LiPF is adopted6EC and DMC (1:1, v/v) are prepared into 1mol/L mixed solution as electrolyte, and a polypropylene microporous membrane is selected as a diaphragm to assemble the R2032 type button cell.
And carrying out a constant-current charge and discharge experiment on the obtained simulated battery, testing the cycle performance of the lithium ion battery, limiting the charge and discharge voltage to be 3.0-4.3V, and controlling the charge and discharge current density to be 200 mA/g. The electrochemical performance of the battery is tested by using a Land tester (blue electronic corporation, Wuhan City), the test condition is room temperature, and the lithium ion battery provided by the embodiment has the specific discharge capacity of 188mAh/g for the first time, the specific discharge capacity of 180mAh/g after 100 times of cyclic charge and discharge, the capacity retention rate of 95.7 percent and better cycle performance.
Comparative example 1
Nickel sulfate, cobalt sulfate and aluminum sulfate are mixed according to a molar ratio of 0.81: 0.16: 0.05 is dissolved in deionized water, and the mixture is subjected to coprecipitation reaction for 120 hours at 60 ℃ under the conditions that the stirring speed is 700r/min and the pH value is 11.0, so as to obtain a precursor Ni of the anode material0.8Co0.15Al0.05(OH)2。
Precursor Ni of positive electrode material0.8Co0.15Al0.05(OH)2And lithium hydroxide in a molar ratio of 1: 1.05, and sintering at 750 ℃ for 10 hours to obtain ternary cathode material particles LiNi0.8Co0.15Al0.05O2。
10g of ternary positive electrode material particles LiNi0.8Co0.15Al0.05O2Dispersing in 5g of mixed solvent consisting of deionized water and ethanol, and uniformly stirring to obtain a mixed solution. YPO is prepared4Adding into the mixed solution to obtain YPO4Accounting for 0.5 wt% of the ternary cathode material, and stirring and reacting for 2 hours at room temperature. Stirring speed of the stirring reaction is 150r/min, ammonia water is dripped to adjust pH of the stirring reaction to be 11, and the ternary cathode material of hydroxide with the yttrium uniformly coated on the outer layer is obtained. Then, the ternary cathode material of which the outer layer was uniformly coated with yttrium hydroxide was filtered, washed with deionized water, and dried in a forced air drying oven at 125 ℃ for 5 hours. And then, carrying out heat treatment for 6h in a muffle furnace at 500 ℃ to obtain the ternary cathode material with the outer layer uniformly coated with the yttrium oxide.
Uniformly coating the outer layer with the yttrium oxide ternary cathode material according to the mass ratio of 0.1: 1 is dispersed in deionized water and washed with stirring. The stirring speed is 150r/min, and the stirring time is 1 h. After the washing was completed, the washed material was placed in a forced air drying oven and dried at 120 ℃ for 6 hours. Then, the steel was tempered in a muffle furnace at 400 ℃ for 6 hours. And cooling to room temperature, taking out, and grinding to obtain the modified ternary cathode material.
Mixing the modified ternary positive electrode material, conductive carbon black Super-P and a binder (polyvinylidene fluoride) according to the weight ratio of 80: 10: 10, adding a proper amount of additive N-methyl pyrrolidone (NMP), then uniformly coating on an aluminum foil current collector, carrying out vacuum drying and rolling to prepare a positive plate, and adopting a lithium plate as a negative plate and LiPF6EC and DMC (1:1, v/v) are prepared into 1mol/L mixed solution as electrolyte, and a polypropylene microporous membrane is selected as a diaphragm to assemble the R2032 type button cell.
And carrying out a constant-current charge and discharge experiment on the obtained simulated battery, and testing the cycle performance of the lithium ion battery, wherein the charge and discharge voltage is limited to 3.0-4.3V, and the charge and discharge current density is 200 mA/g. The electrochemical performance of the battery is tested by using a Land tester (blue electronic corporation, Wuhan City), and the test condition is room temperature, so that the first discharge specific capacity of the lithium ion battery provided by the comparative example is 194mAh/g, the discharge specific capacity after 100 times of cyclic charge and discharge is 160mAh/g, and the capacity retention rate is 82.4%.
It can be seen from the above examples and comparative examples that, after a precursor of a positive electrode material is obtained, nano alumina is mixed with the precursor of the positive electrode material and a lithium salt, and then sintering is performed to obtain ternary positive electrode material particles. The method for adding aluminum is beneficial to improving the specific capacity and the cycle performance of the material. In addition, the specific detergent is further washed after the heat treatment, so that the influence of valence change of nickel element in the ternary positive electrode material on the electrochemical performance of the material due to the conventional water washing of the ternary positive electrode material is avoided, and finally, the lithium ion battery prepared from the modified ternary positive electrode material has high specific capacity and excellent cycle performance.
Experimental results show that the first charge-discharge specific capacity of the lithium ion battery prepared by the modified ternary cathode material is not lower than 180mAh/g under the conditions that the charge-discharge voltage is 3.0-4.3V and the charge-discharge current density is 200 mA/g; after the charge and the discharge are carried out for 100 times in a circulating manner, the discharge specific capacity is not lower than 170mAh/g, the capacity retention rate is not lower than 90%, and the cycle performance is better.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A modified ternary cathode material comprising:
ternary positive electrode material particles and a protective layer coated on the outer surfaces of the ternary positive electrode material particles;
the ternary cathode material particles are composed of a ternary cathode material, and the ternary cathode material is LiNi0.8Co0.15Al0.05O2、LiNi0.6Co0.2Mn0.15 Al0.05O2Or LiNi0.8Co0.05Mn0.1 Al0.05O2；
In the ternary cathode material particles, the content of Al is gradually reduced from the outer surface to the inner part of the ternary cathode material particles;
the ternary cathode material particles are formed by tightly stacking primary particles into secondary particles; the primary particles are spherical, and the particle size of the primary particles is 200-300 nm; the particle size of the secondary particles is 13-15 mu m;
the preparation method of the modified ternary cathode material comprises the following steps:
A) mixing the precursor of the anode material, nano alumina and a lithium compound, and sintering to obtain ternary anode material particles;
the precursor of the positive electrode material is Ni0.8Co0.15(OH)2、Ni0.6Co0.2Mn0.15(OH)2Or Ni0.8Co0.05Mn0.1(OH)2；
B) Mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain a ternary cathode material with a coating structure;
C) and carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
2. The modified ternary positive electrode material according to claim 1, wherein the component of the protective layer is an oxide of a metal or a phosphate of a metal.
3. A method of preparing the modified ternary cathode material of claim 1, comprising:
A) mixing the precursor of the anode material, nano alumina and a lithium compound, and sintering to obtain ternary anode material particles;
the precursor of the positive electrode material is Ni0.8Co0.15(OH)2、Ni0.6Co0.2Mn0.15(OH)2Or Ni0.8Co0.05Mn0.1(OH)2；
B) Mixing a metal compound with the solution of the ternary cathode material particles, and reacting under the condition that the pH value is 7-13 to obtain a ternary cathode material with a coating structure;
C) and carrying out heat treatment on the ternary cathode material with the coating structure to obtain the modified ternary cathode material.
4. The preparation method according to claim 3, wherein the molar ratio of the positive electrode material precursor to the nano alumina to the lithium compound is 0.9-1: 0.01-0.1: 1.0 to 1.07.
5. The preparation method according to claim 3, wherein the sintering temperature is 600-900 ℃, and the sintering time is 6-20 h.
6. The preparation method according to claim 3, wherein the metal compound comprises one or more of metal oxide, metal halide, metal phosphate, metal sulfate, metal nitrate, metal chloride and metal organic salt;
The metal compound accounts for 0.5-2 wt% of the ternary cathode material particles.
7. The method of claim 6, wherein the metal oxide is selected from Al2O3、ZnO、ZrO2、TiO2One or more of the above;
the metal halide is selected from AlCl3、ZrCl4、AlF3And SrBr2One or more of the above;
the metal phosphate is selected from AlPO4And/or YPO4；
The metal sulfate is selected from Al2(SO4)3、Zr(SO4)2And SrSO4One or more of the above;
the metal nitrate is selected from Al (NO)3)3、Sr(NO3)2And Zr (NO)3)4One or more of the above;
the metal chloride is selected from AlCl3、YCl3And SrCl2One or more of the above;
the metal organic salt is selected from one or more of tetrabutyl titanate, aluminum isopropoxide and ethyl orthosilicate.
8. The method according to claim 3, wherein the heat treatment temperature is 300 to 600 ℃ and the heat treatment time is 3 to 6 hours.
9. The method according to claim 3, wherein after the heat treatment, the method further comprises washing and tempering the heat-treated material;
the detergent adopted by washing comprises one or more of water, alcohol organic matters and surfactants;
the tempering temperature is 300-600 ℃; the tempering time is 2-8 h.
10. A lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, and is characterized in that the positive electrode comprises the modified ternary positive electrode material of any one of claims 1 to 2 or the modified ternary positive electrode material prepared by the preparation method of any one of claims 3 to 9.
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