CN108807918B - Surface-coated composite lithium-rich manganese-based cathode material and preparation method thereof - Google Patents

Surface-coated composite lithium-rich manganese-based cathode material and preparation method thereof Download PDF

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CN108807918B
CN108807918B CN201810623442.XA CN201810623442A CN108807918B CN 108807918 B CN108807918 B CN 108807918B CN 201810623442 A CN201810623442 A CN 201810623442A CN 108807918 B CN108807918 B CN 108807918B
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lithium
rich manganese
manganese
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CN108807918A (en
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郭华军
孟凡博
王志兴
王接喜
李新海
张晓明
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Central South University
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    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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Abstract

The invention discloses a tungsten oxide β -WO2.9The lithium-rich manganese-based layered positive electrode material for coating the lithium ion battery and the preparation method thereof, wherein the tungsten oxide comprises β -WO2.9In addition, there is a small amount of WO3、WO2.72And WO2Lithium-rich manganese-based cathode material L i [ L i ]xNiyCo1‑x‑y‑zMnz]O2Mixing the raw materials, and coating β -WO2.9The invention utilizes tungsten oxide β -WO2.9The unique structural characteristic greatly improves the first coulombic efficiency of the lithium ion battery anode material, improves the electrochemical stability and structural stability of the lithium ion battery anode material, obviously improves the cycle stability of the lithium ion battery anode material, and has simple manufacturing process and low cost.

Description

Surface-coated composite lithium-rich manganese-based cathode material and preparation method thereof
Technical Field
The invention belongs to the field of lithium ion battery cathode materials, and particularly relates to a surface-coated composite lithium-rich manganese-based cathode material and a preparation method thereof.
Background
The lithium-rich manganese-based anode material has good application prospect, the theoretical specific discharge capacity of the lithium-rich manganese-based anode material reaches 300mAh/g, which is almost about twice of the actual capacity of the current commercialized anode material, and meanwhile, compared with the common lithium cobaltate and nickel cobalt manganese ternary system anode material, the lithium-rich manganese-based anode material which takes Mn element as a main body has low price and good safety. Therefore, the lithium-rich manganese-based positive electrode material is considered as an ideal choice for the next generation of power lithium ion batteries. However, the material has high initial irreversible capacity and poor cycle and rate performance, and particularly, the discharge medium voltage is continuously reduced in the charge-discharge cycle process, so that the practical application of the material is hindered.
The coating method generally adopts one or more inert substances or conductive substances to form a coating layer on the surface of the original material to protect the surface of the original material from being corroded by electrolyte, reduce the interface impedance of an electrode/electrolyte and also achieve the effects of inhibiting oxygen loss and crystal phase transformation of the lithium-rich manganese-based anode material in the circulating process, so that the modification treatment of the lithium-rich manganese-based anode material by adopting the coating has a great effect on the improvement of the electrochemical performance of the material. At present, phosphate or inert oxide is mostly adopted as a coating layer, but the defects of reduced first discharge capacity of the coated material and the like exist.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a coating β -WO2.9The lithium-rich manganese-based positive electrode material and the preparation method thereof.
The technical scheme of the invention is as follows:
the surface-coated composite lithium-rich manganese-based positive electrode material is characterized in that the lithium-rich manganese-based positive electrode material L i [ L i ]xNiyCo1-x-y-zMnz]O2Is prepared from raw materials, wherein x is more than 0 and less than 1, y is more than 0 and less than 0.4, z is more than 0.4 and less than 1, and the surface is coated with β -WO2.9And (4) coating the material.
Preferably, β -WO2.9Is rich in lithium manganese based anode material L i [ L i ]xNiyCo1-x-y-zMnz]O20.5 to 10% by mass.
Preferably, the coating layer also contains a small amount of WO2.72And/or WO3。
The invention also provides a preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material, which is characterized by comprising the following steps of:
1) dispersing one or more of tungstic acid or tungstate in an ammonia water solution, adding urea after uniform dispersion to prepare an aqueous solution of an intermediate IRT, and preparing a raw material lithium-rich manganese-based anode material L i [ L i ]xNiyCo1-x-y-zMnz]O2Dispersing into the obtained IRT aqueous solutionObtaining suspension;
2) after the suspension obtained in the step 1 is freeze-dried for a certain time, the suspension is calcined and heat-preserved under the atmosphere of ammonia gas and at a certain pressure and temperature to obtain the suspension with the surface coated with β -WO2.9The material is a lithium-rich manganese-based positive electrode material.
Preferably, in the step 1), the dispersing mode is stirring, and the stirring condition is room temperature, the stirring speed is 600-900 r/min, and the stirring time is 20-40 min.
Preferably, in the step 2), the freeze drying time is 48-72 hours, preferably, the gas pressure in the furnace tube is controlled between 5-10 mm water column of atmospheric pressure in the ammonia gas atmosphere, the calcination is carried out for 5-6 hours at the temperature of 450-550 ℃, and then the heat preservation is carried out for 5-6 hours at the temperature of 550-650 ℃.
Preferably, the tungstate is one or both of ammonium tungstate and ammonium metatungstate.
The invention also provides a surface lithium-rich manganese-based positive electrode material L i [ L i ]xNiyCo1-x-y-zMnz]O2The preparation method comprises the following steps:
a) dispersing manganese salt, cobalt salt and nickel salt in deionized water, and stirring for 1-3 h at the stirring speed of 600-900 r/min, wherein the total concentration of metal ions is 2 mol/L;
b) adding an ammonium bicarbonate solution and a sodium carbonate solution into the solution obtained in the step a) under the condition that the stirring speed is 600-900 r/min, then continuously stirring for 2-4 h until the reaction is finished, centrifuging, washing and drying by using ethanol and deionized water to obtain a carbonate precursor, wherein the concentrations of the ammonium bicarbonate solution and the ammonium carbonate solution are 1.5-6 mol/L;
c) fully mixing the precursor obtained in the step b) with a lithium source, then putting the mixture into a tube furnace, calcining for 5-6 h at 400-500 ℃, and then continuously heating to 800-950 ℃ for calcining for 14-18 h to obtain the lithium-rich manganese-based layered material, wherein the molar weight ratio of the total molar weight of nickel, cobalt and manganese to the molar weight of lithium is 1: 1.50-1.59.
Preferably, the lithium source is one or more than two of lithium nitrate, lithium acetate, lithium carbonate or lithium hydroxide; the manganese salt is one or more than two of manganese nitrate, manganese acetate, manganese chloride or manganese sulfate; the nickel salt is one or more than two of nickel nitrate, nickel acetate, nickel chloride or nickel sulfate; the cobalt salt is one or more than two of cobalt nitrate, cobalt acetate, cobalt chloride or cobalt sulfate.
Tungsten oxide β -WO obtained by the technical scheme of the invention2.9Due to the unique point defect structure, more lithium insertion vacancies can be provided, so that the specific discharge capacity of the lithium-rich manganese-based cathode material is further improved. The coated and modified lithium-rich manganese-based positive electrode material is applied to a lithium ion battery, the performance of the lithium ion battery is remarkably improved at room temperature, the charge-discharge voltage range is 2.0-4.6V, the charge-discharge current is 20mA/g, the first coulombic efficiency is over 87.43%, and the first discharge specific capacity is over 290 mAh/g. The capacity retention rate of 100 cycles under the current density of 200mA/g reaches more than 86.78%.
Compared with the prior art, the invention has the advantages that:
1) the surface-coated composite lithium-rich manganese-based positive electrode material prepared by the invention has the advantages of high specific capacity, good rate capability, long cycle life and the like.
2) The preparation method of the surface-coated composite lithium-rich manganese-based cathode material has the advantages of simple operation, environment-friendly process, good controllability and reproducibility, and suitability for large-scale production.
Drawings
The invention is described in further detail below with reference to the figures and specific embodiments.
Fig. 1 is a scanning electron microscope image of the lithium-rich manganese-based positive electrode material precursor prepared in example 1 of the present invention.
Fig. 2 is a scanning electron microscope image of the lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention.
Fig. 3 is a scanning electron microscope image of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention.
Fig. 4 is a transmission electron microscope image of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention.
Fig. 5 is a comparison graph of XRD curves of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in example 1 of the present invention and the lithium-rich manganese-based positive electrode material prepared in comparative example 1.
Fig. 6 is a comparison graph of the first charge-discharge curves of the lithium-ion battery made of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in example 2 of the present invention and the lithium-ion battery made of the lithium-rich manganese-based positive electrode material prepared in proportion.
Fig. 7 is a comparison graph of cycle performance curves of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in example 3 of the present invention and a lithium ion battery prepared from the lithium-rich manganese-based positive electrode material prepared in proportion.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specified, the reagents and materials used in the present invention are commercially available products or products obtained by a known method.
Example 1:
a surface-coated composite lithium-rich manganese-based positive electrode material is represented by the chemical formula of L i [ L i ]0.2Mn0.54Ni0.13Co0.13]O2The outer surface of the lithium-rich manganese-based cathode material with the layered structure is coated with β -WO2.9In example 1, the coating amount was β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2The mass ratio of (B) is 1%.
The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material comprises the following specific steps:
(1) MnSO is weighed according to the mol ratio of Mn, Ni and Co being 0.54: 0.134·H2O，NiSO4·6H2O andCoSO4·7H2o is dispersed in deionized water, 4 mol/L NH is added after the dispersion is completed4HCO3Solution and 1.5 mol/L of Na2CO3Fully stirring the solution until the reaction is finished, and mixing the obtained precursor material with excess L i2CO3Fully grinding in a mortar, putting into a crucible for heat treatment, firstly preserving heat for 6h at 500 ℃, and then preserving heat for 16h at 900 ℃ (the heating rate is 5 ℃/min), thus obtaining the lithium-rich manganese-based cathode material and obtaining Mn0.54Ni0.13Co0.13(CO3)0.8And (3) precursor. 5g of Mn are weighed0.54Ni0.13Co0.13(CO3)0.8Precursors and 2.370g of analytically pure L i2CO3Fully grinding in a mortar to obtain the element composition L i (L i)0.2Mn0.54Ni0.13Co0.13]O2A mixture of (a). As shown in FIG. 1, Mn was prepared in this example0.54Ni0.13Co0.13(CO3)0.8In the scanning electron microscope image of the precursor, the obtained precursor is spherical, the diameter is about 10-20 mu m, the shape is uniform, and the surface is smooth.
(2) Putting the powder obtained in the step 1 into a crucible for heat treatment, raising the temperature to 500 ℃ at the speed of 5 ℃/min according to heat treatment parameters, preserving the heat for 6h, then continuing raising the temperature to 900 ℃ at the speed of 5 ℃/min, preserving the heat for 16h, and cooling along with the furnace to obtain the lithium-rich manganese-based layered positive electrode material L i [ L i ] with fine granularity0.2Mn0.54Ni0.13Co0.13]O2As shown in FIG. 2, L i [ L i ] obtained in this example0.2Mn0.54Ni0.13Co0.13]O2In the scanning electron microscope image, the obtained layered material is spherical, the diameter is about 10 mu m, and the shape and the size are relatively uniform.
(3) According to β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2In an amount of 1%, 10.68mg of (NH) was weighed4)6H2W12O40·xH2O is dispersed in 1mol of L-1Aqueous ammonia solution ofAfter uniform dispersion, adding 25.90mg of urea to prepare an intermediate IRT aqueous solution of 20m L, weighing 1g of the positive electrode material prepared in the step (2) to disperse in the IRT aqueous solution, and stirring at room temperature for 30min to obtain a suspension of the tungsten oxide and the lithium-rich manganese-based layered positive electrode material;
(4) freeze-drying the slurry obtained in the step (3) for 48h, placing the slurry in a tube furnace, calcining the slurry in the furnace tube at the temperature of 450 ℃ for 6h under the condition that the gas pressure in the furnace tube is controlled at 10mm water column of atmospheric pressure in the atmosphere of ammonia gas, and then preserving the heat at the temperature of 650 ℃ for 6h to obtain β -WO2.9Fig. 3 shows a scanning electron microscope image of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in this example, and it can be seen from the image that the surface of the material becomes smoother after the surface coating, fig. 4 shows a transmission electron microscope image of the surface-coated composite lithium-rich manganese-based positive electrode material prepared in this example, and β -WO2.9Uniformly coated on the lithium-rich manganese-based layered cathode material and a small amount of WO2.72、WO3、WO2The coating is coated on the surface of the material, and the thickness of the coating is about 20 nm.
When the surface-coated composite lithium-rich manganese-based positive electrode material of the embodiment is subjected to an X-ray diffraction test, an XRD curve is shown as a curve (b) in figure 5, and related data are shown as table 1. by analyzing XRD data, the peak intensity of the coated material is not obviously changed, but β -WO appears in the treated material2.9And WO2.72Peak of isotungsten oxide, Explanation β -WO2.9Successfully coated on the surface of the material. Meanwhile, the a value and the c value of the treated material have no obvious change, but the I (003)/I (104) value is obviously increased, which shows that the laminated structure of the coated material is more stable and the ion mixing is more uniform.
Example 2:
a surface-coated composite lithium-rich manganese-based positive electrode material is represented by the chemical formula of L i [ L i ]0.2Mn0.54Ni0.13Co0.13]O2The outer surface of the lithium-rich manganese-based cathode material with the layered structure is coated with β -WO2.9In example 2, the coating amount was β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2The mass ratio of (B) is 3%.
The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material comprises the following specific steps:
(1) MnSO is weighed according to the mol ratio of Mn, Ni and Co being 0.54: 0.134·H2O，NiSO4·6H2O and CoSO4·7H2O is dispersed in deionized water, and 6 mol/L NH is added after the dispersion is completed4HCO3Solution and 3 mol/L mol of Na2CO3Fully stirring the solution until the reaction is finished, and mixing the obtained precursor material with excess L i2CO3Fully grinding in a mortar, putting into a crucible for heat treatment, firstly preserving heat for 6h at 500 ℃, and then preserving heat for 16h at 900 ℃ (the heating rate is 5 ℃/min), thus obtaining the lithium-rich manganese-based cathode material and obtaining Mn0.54Ni0.13Co0.13(CO3)0.8 precursor. 5g of Mn are weighed0.54Ni0.13Co0.13(CO3)0.8The precursor and 2.370g of analytically pure L i2CO3 were fully ground in a mortar to obtain an elemental composition of L i [ L i ]0.2Mn0.54Ni0.13Co0.13]O2A mixture of (a).
(2) Putting the powder obtained in the step 1 into a crucible for heat treatment, heating the heat treatment parameter to 450 ℃ at a speed of 5 ℃/min, preserving the heat for 6h, then continuously heating to 900 ℃ at a speed of 5 ℃/min, preserving the heat for 16h, and cooling along with the furnace to obtain the lithium-rich manganese-based layered positive electrode material L i [ L i ] with fine granularity0.2Mn0.54Ni0.13Co0.13]O2。
(3) According to β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2In a mass ratio of 3%, 32.32mg of H was weighed2WO4Dispersed in 1mol of L-1Adding 77.70mg of urea after even dispersion to the ammonia water solution to prepare an intermediate IRT aqueous solution with the thickness of 20m L, weighing 1g of the anode material prepared in the step (2) and dispersing the anode material in the IRT aqueous solution, and performing ultrasonic treatment for 60min to obtain β -WO2.9Suspension of the lithium-rich manganese-based layered positive electrode material;
(4) freeze-drying the slurry obtained in the step (3) for 72h, placing the slurry in a tube furnace, controlling the gas pressure in the tube furnace to be 8mm water column with atmospheric pressure in the ammonia gas atmosphere, calcining the slurry at 500 ℃ for 6h, and then preserving the heat at 650 ℃ for 6h to obtain β -WO2.9The coated lithium-rich manganese-based positive electrode material,
the lithium-ion battery prepared from the surface-coated composite lithium-rich manganese-based positive electrode material of the embodiment is subjected to electrochemical performance test, and the first charge-discharge curve of the lithium-ion battery is shown in (b) in fig. 6. from the graph, it can be found that the first irreversible capacity of the modified material is reduced from 85.85mAh/g to 44.98mAh/g, the first coulombic efficiency of the material is increased from 74.62% to 87.43%, and meanwhile, the first discharge capacity is increased from 252.40mAh/g to 305.86mAh/g, which shows β -WO 382.9Due to the structural particularity of the coating layer, more pores can be provided to be used as vacancies for lithium ion insertion and extraction in the charging and discharging processes, and the migration rate of lithium ions in the lithium ion battery is improved, so that the first efficiency of the material is obviously improved, and the first irreversible capacity loss is reduced.
Example 3:
a surface-coated composite lithium-rich manganese-based positive electrode material is represented by the chemical formula of L i [ L i ]0.2Mn0.54Ni0.13Co0.13]O2The outer surface of the lithium-rich manganese-based cathode material with the layered structure is coated with β -WO2.9In example 3, the coating amount was β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2The mass ratio of (B) is 5%.
The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material comprises the following specific steps:
a surface-coated composite lithium-rich manganese-based positive electrode material is represented by the chemical formula of L i [ L i ]0.2Mn0.54Ni0.13Co0.13]O2The outer surface of the lithium-rich manganese-based cathode material with the layered structure is coated with β -WO2.9In example 3, the coating amount was β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2The mass ratio of (B) is 5%.
The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material comprises the following specific steps:
(1) MnSO is weighed according to the mol ratio of Mn, Ni and Co being 0.54: 0.134·H2O，NiSO4·6H2O and CoSO4·7H2O is dispersed in deionized water, and 6 mol/L NH is added after the dispersion is completed4HCO3Solution and 3 mol/L mol of Na2CO3Fully stirring the solution until the reaction is finished, and mixing the obtained precursor material with excess L i2CO3Fully grinding in a mortar, putting into a crucible for heat treatment, firstly preserving heat for 6h at 500 ℃, and then preserving heat for 16h at 900 ℃ (the heating rate is 5 ℃/min), thus obtaining the lithium-rich manganese-based cathode material and obtaining Mn0.54Ni0.13Co0.13(CO3)0.8And (3) precursor. 5g of Mn are weighed0.54Ni0.13Co0.13(CO3)0.8Precursors and 2.370g of analytically pure L i2CO3Fully grinding in a mortar to obtain the element composition L i (L i)0.2Mn0.54Ni0.13Co0.13]O2A mixture of (a).
(2) Putting the powder obtained in the step 1 into a crucible for heat treatment, raising the temperature to 500 ℃ at the speed of 5 ℃/min according to heat treatment parameters, preserving the heat for 6h, then continuing raising the temperature to 900 ℃ at the speed of 5 ℃/min, preserving the heat for 16h, and cooling along with the furnace to obtain the lithium-rich manganese-based layered positive electrode material L i [ L i ] with fine granularity0.2Mn0.54Ni0.13Co0.13]O2。
(3) According to β -WO2.9/Li[Li0.2Mn0.54Ni0.13Co0.13]O2Is 5%, 53.39mg of (NH)4)6H2W12O40·xH2O is dispersed in 1mol of L-1Adding 129.50mg of urea after uniform dispersion into the ammonia water solution to prepare an intermediate IRT aqueous solution of 20m L, weighing 1g of the positive electrode material prepared in the step (2), dispersing the positive electrode material into the IRT aqueous solution, and performing ultrasonic treatment for 60min to obtain β -WO2.9Suspension of the lithium-rich manganese-based layered positive electrode material;
(4) freeze-drying the slurry obtained in the step (3) for 72h, placing the slurry in a tube furnace, controlling the gas pressure in the tube furnace to be 8mm water column with the atmospheric pressure in the ammonia atmosphere, calcining the slurry at 550 ℃ for 6h, and then preserving the heat at 600 ℃ for 6h to obtain β -WO2.9The coated lithium-rich manganese-based positive electrode material,
the lithium-ion battery prepared from the surface-coated composite lithium-rich manganese-based positive electrode material of the embodiment is subjected to performance test, the cycle performance under high current density (0.5C) is shown as a curve (b) in fig. 7, the cycle performance under 0.5C is 100 circles, the first discharge specific capacity of the material is 260.01mAh/g, the capacity retention rate is 86.78%, the cycle stability of the material is good, β -WO2.9The coating layer effectively improves the structural stability and the electrochemical performance of the lithium-rich manganese-based cathode material.
Comparative example:
(1) preparing a lithium-rich manganese-based positive electrode material: MnSO is weighed according to the mol ratio of Mn, Ni and Co being 0.54: 0.134·H2O，NiSO4·6H2O and CoSO4·7H2O is dispersed in deionized water, 4 mol/L NH is added after the dispersion is completed4HCO3Solution and 1.5 mol/L of Na2CO3Fully stirring the solution until the reaction is finished, and mixing the obtained precursor material with excess L i2CO3Fully grinding in a mortar, putting into a crucible for heat treatment, firstly preserving heat for 6h at 500 ℃, and then preserving heat for 16h at 900 ℃ (the heating rate is 5 ℃/min), thus obtaining the lithium-rich manganese-based cathode material and obtaining Mn0.54Ni0.13Co0.13(CO3)0.8And (3) precursor. 5g of Mn are weighed0.54Ni0.13Co0.13(CO3)0.8Precursors and 2.370g of analytically pure L i2CO3Fully grinding in a mortar to obtain the element composition L i (L i)0.2Mn0.54Ni0.13Co0.13]O2A mixture of (a).
(2) And (3) sintering: putting the powder obtained in the step 1 into a crucible for heat treatment, raising the temperature to 500 ℃ at the speed of 5 ℃/min and preserving the heat for 6h according to heat treatment parameters, then continuing raising the temperature to 900 ℃ at the speed of 5 ℃/min and preserving the heat for 16h, and cooling along with the furnace to obtain the powderTo a lithium-rich manganese-based layered cathode material L i [ L i ] with fine granularity0.2Mn0.54Ni0.13Co0.13]O2。
The lithium-rich manganese-based positive electrode material of the present comparative example was subjected to an X-ray diffraction test, and its XRD curve is shown as the (a) curve in fig. 5, and its associated data are shown in table 1. The XRD data shows that the value of I (003)/I (104) is lower, which indicates that the material before coating has poor layered structure and poor ion mixing. When the lithium-rich manganese-based cathode material of the comparative example is prepared into a lithium ion battery and subjected to electrochemical performance test, the first charge-discharge curve of the lithium-rich manganese-based cathode material is shown in (a) in fig. 6, the first irreversible capacity of the raw material is as high as 85.85mAh/g, the first coulombic efficiency is only 74.62%, and the first irreversible capacity is large. The cycle performance under the large current density (0.5C) is shown as a curve (a) in fig. 7, the capacity retention rate of the material is poor, the first discharge specific capacity of the material is 237.01mAh/g after 100 cycles under 0.5C, but the capacity retention rate is only 23.63%, and the cycle stability of the material is poor.
TABLE 1
Figure GDA0002467251740000071
The above examples are one of the more preferred embodiments of the present invention, and general changes and substitutions within the scope of the present invention by those skilled in the art are intended to be included within the scope of the present invention.

Claims (8)

1. A surface-coated composite lithium-rich manganese-based positive electrode material is characterized in that:
in the lithium-rich manganese-based anode material L i [ L i ]xNiyCo1-x-y-zMnz]O2Is coated with β -WO2.9A coating of material, wherein: 0<x<1，0<y<0.4，0.4<z<1，
β-WO2.9Is rich in lithium manganese based anode material L i [ L i ]xNiyCo1-x-y-zMnz]O20.5 to 10% by mass.
2. The surface-coated composite lithium-rich manganese-based positive electrode material as claimed in claim 1, wherein: the coating also contains a certain amount of WO2.72、WO2And/or WO3。
3. The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material as claimed in any one of claims 1 to 2, characterized by comprising the following steps:
1) adding one or more of tungstic acid or tungstate into an ammonia water solution, uniformly mixing, adding urea to prepare an aqueous solution of an intermediate IRT, and adding a raw material lithium-rich manganese-based anode material L i [ L i ]xNiyCo1-x-y-zMnz]O2Dispersing into the obtained IRT aqueous solution to obtain a suspension;
2) freeze-drying the suspension obtained in the step 1) for a certain time, calcining and preserving heat under the atmosphere of ammonia gas and at a certain pressure and temperature to obtain the suspension with the surface coated with β -WO2.9The material is a lithium-rich manganese-based positive electrode material.
4. The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material as claimed in claim 3, wherein in the step 1), the dispersion method is stirring, the stirring condition is room temperature, the stirring speed is 600-900 r/min, and the stirring time is 20-40 min.
5. The preparation method of the surface-coated composite lithium-rich manganese-based positive electrode material as claimed in claim 3, wherein in the step 2), the freeze-drying time is 48-72 h.
6. The method for preparing the surface-coated composite lithium-rich manganese-based positive electrode material according to claim 3, wherein the tungstate is one or both of ammonium tungstate and ammonium metatungstate.
7. The method for preparing the surface-coated composite lithium-rich manganese-based positive electrode material as claimed in claim 3, wherein the surface-coated composite lithium-rich manganese-based positive electrode material is prepared by a method comprisingThen, the raw material lithium-rich manganese-based cathode material L i [ L i ]xNiyCo1-x-y-zMnz]O2The preparation method comprises the following steps:
a) dispersing manganese salt, cobalt salt and nickel salt in deionized water, and stirring for 1-3 h at the stirring speed of 600-900 r/min, wherein the total concentration of metal ions is 2 mol/L;
b) adding an ammonium bicarbonate solution and a sodium carbonate solution into the solution obtained in the step a) under the condition that the stirring speed is 600-900 r/min, then continuously stirring for 2-4 h until the reaction is finished, centrifuging, washing and drying by using ethanol and deionized water to obtain a carbonate precursor, wherein the concentrations of the ammonium bicarbonate solution and the ammonium carbonate solution are 1.5-6 mol/L respectively;
c) fully mixing the precursor obtained in the step b) with a lithium source, then putting the mixture into a tube furnace, calcining for 5-6 h at 400-500 ℃, and then continuously heating to 800-950 ℃ for calcining for 14-18 h to obtain the lithium-rich manganese-based layered material, wherein the molar weight ratio of the total molar weight of nickel, cobalt and manganese to the molar weight of lithium is 1: 1.50-1.59.
8. The method for preparing the surface-coated composite lithium-rich manganese-based positive electrode material as claimed in claim 7, wherein the lithium source is one or more of lithium nitrate, lithium acetate, lithium carbonate or lithium hydroxide; the manganese salt is one or more than two of manganese nitrate, manganese acetate, manganese chloride or manganese sulfate; the nickel salt is one or more than two of nickel nitrate, nickel acetate, nickel chloride or nickel sulfate; the cobalt salt is one or more than two of cobalt nitrate, cobalt acetate, cobalt chloride or cobalt sulfate.
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