CN114649522A - Mo-doped Fe2O3Coated lithium-rich manganese-based positive electrode material and preparation method thereof - Google Patents

Mo-doped Fe2O3Coated lithium-rich manganese-based positive electrode material and preparation method thereof Download PDF

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CN114649522A
CN114649522A CN202210482585.XA CN202210482585A CN114649522A CN 114649522 A CN114649522 A CN 114649522A CN 202210482585 A CN202210482585 A CN 202210482585A CN 114649522 A CN114649522 A CN 114649522A
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陈帅
丁飞
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    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • 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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    • H01M2004/028—Positive electrodes

Abstract

The invention provides Mo-doped Fe2O3A coated lithium-rich manganese-based positive electrode material and a preparation method thereof relate to the technical field of energy storage materials. Compared with the prior art, the anode material combines molybdenum doping and ferric oxide modification, and after double-effect modification, the cycle stability and the multiplying power of the lithium-rich manganese-based anode material are improvedPerformance, first discharge specific capacity and other electrochemical performances.

Description

Mo-doped Fe2O3Coated lithium-rich manganese-based positive electrode material and preparation method thereof
Technical Field
The invention relates to the technical field of energy storage materials, in particular to Mo-doped Fe2O3A coated lithium-rich manganese-based positive electrode material and a preparation method thereof.
Background
Lithium ion batteries, because of their high energy and power densities, are widely used in the fields of consumer electronics, electric vehicles, energy storage, and the like. Conventional positive electrode materials, e.g. layers, for lithium ion batteriesLiCoO-like2Spinel type LiMn2O4And olivine type LiFePO4The discharge specific capacity is lower, the cycle performance is poorer, and the requirements can not be met. The lithium-rich manganese-based positive electrode material has higher energy density and specific capacity (>250mAh g) is an ideal substitute of the traditional cathode material, and is also one of the main directions of the current cathode material research. However, the commercial application is limited by severe first cycle irreversible capacity loss, irreversible structural changes during cycling resulting in voltage decay, rate capability and poor cycling performance.
Based on the above, the novel lithium-rich manganese-based positive electrode material has important significance.
Disclosure of Invention
The invention aims to provide Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based positive electrode material can obviously improve the first discharge specific capacity, the cycling stability and the rate capability of a lithium-rich layer.
Another object of the present invention is to provide a Mo-doped Fe2O3The lithium-rich manganese-based positive electrode material is coated, and has all the beneficial effects.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
In one aspect, the present invention provides a Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based positive electrode material mainly comprises the following steps:
mixing NiCl2、CoCl2And MnCl2Dissolving in water to obtain a first mixed solution; NaOH and Na2MoO4Mixing to obtain precipitant; mixing the mixed solution I, a precipitator and ammonia water under the protection of argon to obtain mixed solution II, and stirring the mixed solution II to perform solid-liquid separation to obtain molybdenum-manganese hydroxide precipitate; washing the molybdenum-manganese containing hydroxide precipitate, and drying at the temperature of 75-85 ℃ for 11-13 h to prepare a precursor;
mixing the precursor with LiOH, mixing with a dispersant I, sequentially grinding and drying, calcining for 4.5-5.5 h at 490-510 ℃, heating to 845-855 ℃, calcining for 23-25 h, and cooling to obtain the Mo-doped lithium-rich manganese-based material;
dispersing the Mo-doped lithium-rich manganese-based material and a dispersant in water, and adding FeCl3Stirring for 1.8-2.2 h, adding alkali for precipitation, and stirring for 4.8-5.2 h to obtain a material; washing the material, and drying for 4.5-5.5 h at 55-65 ℃ to obtain a prefabricated product; and then placing the preform into a tube furnace and firing at 490-510 ℃ for 2.8-3.2 h to obtain the cathode material.
On the other hand, the invention provides Mo-doped Fe2O3The coated lithium-rich manganese-based positive electrode material is prepared by the preparation method.
Mo-doped Fe of the examples of the invention2O3The coated lithium-rich manganese-based positive electrode material and the preparation method thereof have at least the following beneficial effects:
the application provides a Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based cathode material comprises the steps of preparing molybdenum-containing manganese-based hydroxide precipitate by a coprecipitation method, washing to obtain a precursor, mixing the precursor with lithium hydroxide, calcining, and preparing the precursor and ferric chloride together to obtain the cathode material with a pure-phase layered crystal structure. The anode material is doped with molybdenum element, the doped molybdenum element can enter the crystal lattice to replace the main element manganese under the high temperature condition, and the radius of the molybdenum ion is larger than that of the manganese ion, so that the crystal lattice parameter can be enlarged by replacing the manganese element with the molybdenum element, the effect of improving the speed performance is achieved, the oxygen release can be weakened, the crystal structure is stable, and the discharge specific capacity and the cycle performance are effectively improved.
The positive electrode material is coated with compact ferric oxide on the surface, so that the corrosion effect of the electrolyte on the positive electrode material can be effectively inhibited, the stability of the positive electrode material is good, the first coulombic efficiency is high, and the cycle performance and the rate capability of the positive electrode material can be further improved.
Compared with the prior art, the cathode material combines molybdenum doping and ferric oxide modification, and after double-effect modification, the cycle stability, rate capability, first discharge specific capacity and other electrochemical properties of the lithium-rich manganese-based cathode material are improved.
Drawings
To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 is a scanning electron microscope image of a lithium-rich manganese-based positive electrode material prepared in example 1 provided herein;
fig. 2 is an XRD pattern of the lithium-rich manganese-based positive electrode material prepared in example 1 and the comparative example provided in the present application;
fig. 3 is a comparison graph of the first charge and discharge curves of the lithium-rich manganese-based positive electrode materials prepared in the comparative example, example 5 and example 6 at 25 ℃ and 0.1C rate;
FIG. 4 shows the cycle performance test results of the lithium-rich manganese-based positive electrode material prepared in the comparative example and example 5 at 25 ℃ and 0.5C rate;
fig. 5 shows the rate performance test results of the lithium-rich manganese-based positive electrode material prepared in example 5 and comparative example provided in the present application at 25 ℃.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to specific examples.
In one aspect, the present application provides a Mo-doped Fe2O3The lithium-rich manganese-based coated positive electrode material mainly comprises the following steps:
mixing NiCl2、CoCl2And MnCl2Dissolving in water to obtain a first mixed solution; mixing NaOH and Na2MoO4Mixing to obtain precipitant; mixing the mixed solution I, a precipitator and ammonia water under the protection of argon to obtain mixed solution II, and stirring the mixed solution II to perform solid-liquid separation to obtain molybdenum-manganese hydroxide precipitate; washing the molybdenum-manganese containing hydroxide precipitate, and drying at the temperature of 75-85 ℃ for 11-13 h to prepare a precursor;
mixing the precursor with LiOH, mixing with a dispersant I, sequentially grinding and drying, calcining for 4.5-5.5 h at 490-510 ℃, heating to 845-855 ℃, calcining for 23-25 h, and cooling to obtain the Mo-doped lithium-rich manganese-based material;
dispersing the Mo-doped lithium-rich manganese-based material and a dispersant in water, and adding FeCl3Stirring for 1.8-2.2 h, adding alkali for precipitation, and stirring for 4.8-5.2 h to obtain a material; washing the material, and drying for 4.5-5.5 h at 55-65 ℃ to obtain a prefabricated product; and then placing the preform into a tube furnace and firing at 490-510 ℃ for 2.8-3.2 h to obtain the cathode material.
It is noted that the doping amount of the molybdenum element is 0.42%, the coating amount of the iron oxide is 0.5 wt% -13 wt%, and the thickness of the coating layer of the iron oxide is 0.4nm-100 nm.
And after coprecipitation, the molecular formula of the precursor prepared is Mn0.7Ni0.2Co0.1(OH)2The molecular formula of the Mo-doped lithium-rich manganese-based material prepared by calcining is Li1.2Mn0.56Ni0.16Co0.08O2。
In the application, the precursor is mixed with lithium hydroxide and a dispersant I, and is ground and dried at 70 ℃, and the drying time is 8 hours.
According to the application, when the Mo-doped lithium-rich manganese-based material is prepared by calcination, the temperature is raised to a preset temperature at the speed of 5 ℃/min, the temperature is raised to 845-855 ℃ at the speed of 5 ℃/min after calcination, the temperature is kept for 23-25 h, the temperature is lowered to 300 ℃ at the speed of 10 ℃/min, and then the material is naturally cooled to room temperature.
In the application, before the anode material is prepared, the temperature is raised to a preset temperature at the speed of 5 ℃/min during calcination, and after the anode material is fired for 2.8h-3.2h, the temperature is lowered to 300 ℃ at the speed of 10 ℃/min, and then the anode material is naturally cooled to the room temperature.
In this application, NiCl2、CoCl2And MnCl2The molar ratio of (6.5-7.5) to (2: 1).
In the application, the pH of the mixed solution II is 9-11.
In the application, the stirring speed of the mixed solution II is 290-310 rpm, and the stirring temperature is 65 ℃ +/-3 ℃.
In the present application, the precursor and LiOH are reacted with n(Ni+Co+Mn+Mo)/nLiMixing at a ratio of 1: 1.55.
In the present application, the first dispersant is absolute ethyl alcohol.
In the application, the second dispersing agent is polyvinylpyrrolidone.
In the process of the alkali precipitation, NaOH solution of 0.45mol/L-0.55mol/L is added dropwise to form precipitate.
In the application, the mixed solution II is stirred and then subjected to solid-liquid separation in a vacuum filtration mode to obtain molybdenum-manganese hydroxide precipitate.
On the other hand, the application provides Mo-doped Fe prepared by the preparation method2O3And coating the lithium-rich manganese-based positive electrode material. The cathode material combines molybdenum doping and ferric oxide modification, and after double-effect modification, the cycle performance, the stability, the rate capability, the first discharge specific capacity and other electrochemical performances of the lithium-rich manganese-based cathode material are improved.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The purpose of this example is to provide a Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based positive electrode material comprises the following specific steps:
(1) molybdenum-containing manganese-based hydroxide precipitate (Mn)0.7Ni0.2Co0.1(OH)2) The preparation of (1): nickel chloride, cobalt chloride and manganese chloride are mixed according to a molar ratio nMn:nNi:nCoDissolving the mixture in deionized water in a ratio of 7:2:1 to prepare a 1mol/L solution, and performing ultrasonic treatment at room temperature for 15min to obtain a mixed solution I; mixing NaOH and Na2MoO4Mixing (wherein, Na2MoO4As a Mo source, a stoichiometric amount of Na was added in accordance with a doping ratio of 0.42%2MoO4) Carrying out ultrasonic treatment at room temperature for 15min to obtain a precipitator; slowly adding the mixed solution I, the precipitant and the buffer solution into a beaker protected by argon gas by using a peristaltic pump to prepare a mixed solution II, keeping the pH of the mixed solution II within the range of 9.5-10 in the dropping process, controlling the stirring speed to be 300r/min by using a digital display heating type disc magnetic stirrer, controlling the temperature to be 65 +/-1 ℃, and reacting for 10 hours to prepare the molybdenum-containing manganese-based hydroxide precipitate.
(2) Preparing a precursor: and (3) carrying out suction filtration on the molybdenum-containing manganese-based hydroxide precipitate by a circulating water multi-purpose vacuum pump, washing the molybdenum-containing manganese-based hydroxide precipitate to be neutral by deionized water and ethanol, and drying the molybdenum-containing manganese-based hydroxide precipitate in an electric heating forced air drying oven at 80 ℃ for 12 hours to obtain a precursor.
(3) Preparing the Mo-doped lithium-rich manganese-based material: the precursor and battery-grade lithium hydroxide are mixed according to a molar ratio n(Ni+Co+Mn+Mo)/nLiMixing at a ratio of 1:1.55, mixing with absolute ethyl alcohol as a dispersant I, manually grinding in an agate mortar until almost no obvious crystalline fine particles exist, and drying the ground material in a drying oven at 70 ℃ for 8 hours to obtain a mixture (containing a precursor and lithium hydroxide);
and then, putting the mixture into a high-temperature resistance furnace, heating to 500 ℃ at a heating rate of 5 ℃/min in an air atmosphere, keeping calcining for 5h, heating to 850 ℃ at a heating rate of 5 ℃/min, keeping the temperature, calcining for 24h, cooling to 300 ℃ at a speed of 10 ℃/min after calcining, and naturally cooling to room temperature to obtain a 0.42% Mo-doped lithium-rich manganese-based material, which is marked as LMNCO-Mo.
(4) Preparing a positive electrode material: according to Fe2O3: the mass ratio of LMNCO to Mo is 0.5%, 3.0g of LMNCO to Mo powder and 0.01g of polyvinylpyrrolidone (PVPK-30 for short, namely dispersant II) are weighed and dispersed in 30mL of deionized water together, the mixture is stirred by magnetic force to be uniformly dispersed to obtain dispersion liquid, and then 0.05g of FeCl is added into the dispersion liquid at room temperature3·6H2O (99.0%), stirring at 100rpm with a digital display heating type disc magnetic stirrer, and after stirring for 2 hours, dropwise adding an excess NaOH solution (concentration of 0.5mol/L) to form Fe (OH)3Precipitating, and stirring for 5h to obtain the material.
(5) Washing the materials with deionized water for three times, and then carrying out vacuum drying for 5 hours in a vacuum drying oven at the temperature of 60 ℃ to obtain a prefabricated product; and then placing the prefabricated product in a tube furnace in the air atmosphere, heating to 500 ℃ at the heating rate of 5 ℃/min, and then preserving heat for 3 hours to obtain the anode material, which is marked as LMNCO-Mo-0.5F.
Example 2
The purpose of this example is to provide a Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based positive electrode material comprises the following specific steps:
(1) molybdenum-containing manganese-based hydroxide precipitate (Mn)0.7Ni0.2Co0.1(OH)2) The preparation of (1): nickel chloride, cobalt chloride and manganese chloride are mixed according to a molar ratio nMn:nNi:nCoDissolving the mixture in deionized water at a ratio of 6.5:2:1 to prepare a 0.95mol/L solution, and performing ultrasonic treatment at room temperature for 15min to obtain a mixed solution I; mixing NaOH and Na2MoO4Mixing (wherein, Na2MoO4As a Mo source, a stoichiometric amount of Na was added in accordance with a doping ratio of 0.42%2MoO4) Performing ultrasonic treatment at room temperature for 15min to obtain a precipitator; slowly adding the mixed solution I, the precipitant and the buffer solution into a beaker protected by argon gas by using a peristaltic pump to prepare a mixed solution II, keeping the pH of the mixed solution II within the range of 9.0-9.5 in the dropping process, and using the mixed solution IIThe stirring speed of a digital display heating type disc magnetic stirrer is controlled to be 290r/min, the temperature is controlled to be 65 +/-2 ℃, and after reaction is carried out for 10 hours, the molybdenum-containing manganese-based hydroxide precipitate is prepared.
(2) Preparing a precursor: and (3) carrying out suction filtration on the molybdenum-containing manganese-based hydroxide precipitate by a circulating water multi-purpose vacuum pump, washing the molybdenum-containing manganese-based hydroxide precipitate to be neutral by deionized water and ethanol, and drying the molybdenum-containing manganese-based hydroxide precipitate in an electric heating forced air drying oven at 75 ℃ for 11 hours to obtain a precursor.
(3) Preparing the Mo-doped lithium-rich manganese-based material: the precursor and battery-grade lithium hydroxide are mixed according to a molar ratio n(Ni+Co+Mn+Mo)/nLiMixing at a ratio of 1:1.55, mixing with absolute ethyl alcohol as a dispersant I, manually grinding in an agate mortar until almost no obvious crystalline fine particles exist, and drying the ground material in a drying oven at 70 ℃ for 8 hours to obtain a mixture (containing a precursor and lithium hydroxide);
then, putting the mixture in a high-temperature resistance furnace, heating to 495 ℃ at a heating rate of 5 ℃/min in an air atmosphere, keeping calcining for 4.5h, heating to 845 ℃ at a heating rate of 5 ℃/min, keeping the temperature, calcining for 24h, cooling to 300 ℃ at a speed of 10 ℃/min after calcining, and naturally cooling to room temperature to obtain the 0.42% Mo-doped lithium-rich manganese-based material, which is marked as LMNCO-Mo.
(4) Preparing a positive electrode material: according to Fe2O3: the mass ratio of LMNCO to Mo is 0.5%, 3.0g of LMNCO to Mo powder and 0.01g of polyvinylpyrrolidone (PVPK-30 for short, namely dispersant II) are weighed and dispersed in 30mL of deionized water together, the mixture is stirred by magnetic force to be uniformly dispersed to obtain dispersion liquid, and then 0.05g of FeCl is added into the dispersion liquid at room temperature3·6H2O (99.0%), stirring speed was controlled to 90rpm with a digital display heating type disc magnetic stirrer, and after stirring was continued for 1.8h, excess NaOH solution (concentration 0.5mol/L) was added dropwise to form Fe (OH)3Precipitating, and stirring for 4.8h to obtain the material.
(5) Washing the materials with deionized water for three times, and then carrying out vacuum drying for 4.8h in a vacuum drying oven at the temperature of 55 ℃ to obtain a prefabricated product; and then placing the prefabricated product in a tube furnace in the air atmosphere, heating to 490 ℃ at the heating rate of 5 ℃/min, and then preserving heat for 2.8 hours to obtain the anode material, which is marked as LMNCO-Mo-0.5F.
Example 3
The purpose of this example is to provide a Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based positive electrode material comprises the following specific steps:
(1) molybdenum-containing manganese-based hydroxide precipitate (Mn)0.7Ni0.2Co0.1(OH)2) The preparation of (1): nickel chloride, cobalt chloride and manganese chloride are mixed according to a molar ratio nMn:nNi:nCoDissolving the mixture in deionized water at a ratio of 7.5:2:1 to prepare a solution of 1.05mol/L, and performing ultrasonic treatment at room temperature for 15min to obtain a mixed solution I; mixing NaOH and Na2MoO4Mixing (wherein, Na2MoO4As a Mo source, a stoichiometric amount of Na was added in accordance with a doping ratio of 0.42%2MoO4) Carrying out ultrasonic treatment at room temperature for 15min to obtain a precipitator; slowly adding the mixed solution I, the precipitant and the buffer solution into a beaker protected by argon gas by using a peristaltic pump to prepare a mixed solution II, keeping the pH of the mixed solution II within the range of 10.5-11 in the dropping process, controlling the stirring speed to be 310r/min by using a digital display heating type disc magnetic stirrer, controlling the temperature to be 65 +/-3 ℃, and reacting for 10 hours to prepare the molybdenum-containing manganese-based hydroxide precipitate.
(2) Preparing a precursor: and (3) carrying out suction filtration on the molybdenum-containing manganese-based hydroxide precipitate by a circulating water multi-purpose vacuum pump, washing the molybdenum-containing manganese-based hydroxide precipitate to be neutral by deionized water and ethanol, and drying the molybdenum-containing manganese-based hydroxide precipitate for 13 hours at 85 ℃ in an electric heating forced air drying oven to obtain a precursor.
(3) Preparing the Mo-doped lithium-rich manganese-based material: the precursor and battery-grade lithium hydroxide are mixed according to a molar ratio n(Ni+Co+Mn+Mo)/nLiMixing at a ratio of 1:1.55, mixing with absolute ethyl alcohol as a dispersant I, manually grinding in an agate mortar until almost no obvious crystalline fine particles exist, and drying the ground material in a drying oven at 70 ℃ for 8 hours to obtain a mixture (containing a precursor and lithium hydroxide);
then, putting the mixture in a high-temperature resistance furnace, heating to 510 ℃ at a heating rate of 5 ℃/min in an air atmosphere, keeping calcining for 5.5h, heating to 855 ℃ at the heating rate of 5 ℃/min, keeping the temperature, calcining for 25h, cooling to 300 ℃ at a speed of 10 ℃/min after calcining, and naturally cooling to room temperature to obtain the 0.42% Mo-doped lithium-rich manganese-based material, which is marked as LMNCO-Mo.
(4) Preparing a positive electrode material: according to Fe2O3: the mass ratio of LMNCO to Mo is 0.5%, 3.0g of LMNCO to Mo powder and 0.01g of polyvinylpyrrolidone (PVPK-30 for short, namely dispersant II) are weighed and dispersed in 30mL of deionized water together, the mixture is stirred by magnetic force to be uniformly dispersed to obtain dispersion liquid, and then 0.05g of FeCl is added into the dispersion liquid at room temperature3·6H2O (99.0%), stirring speed was controlled to 100rpm with a digital display heating type disc magnetic stirrer, and after stirring was continued for 2.2 hours, an excess NaOH solution (concentration 0.5mol/L) was added dropwise to form Fe (OH)3Precipitating, and stirring for 5.2h to obtain the material.
(5) Washing the materials with deionized water for three times, and then carrying out vacuum drying for 5.5 hours in a vacuum drying oven at the temperature of 65 ℃ to obtain a prefabricated product; and then placing the prefabricated product in a tube furnace in the air atmosphere, heating to 510 ℃ at the heating rate of 5 ℃/min, and then preserving heat for 3.2 hours to obtain the anode material, which is marked as LMNCO-Mo-0.5F.
Example 4
This example differs from example 1 in that Fe2O3: the mass ratio of LMNCO to Mo is 1 percent, and FeCl3·6H2O (99.0%) was added in an amount of 0.101 g.
Example 5
This example differs from example 1 in that Fe2O3: the mass ratio of LMNCO to Mo is 5 percent, and FeCl3·6H2O (99.0%) was added in an amount of 0.507g, and the prepared positive electrode material was designated LMNCO-Mo-5F.
Example 6
This example differs from example 1 in that Fe2O3: the mass ratio of LMNCO to Mo is 9 percent, and FeCl3·6H2O (99.0%) was added in an amount of 0.912g, and the prepared positive electrode material was designated LMNCO-Mo-9F.
Example 7
This example differs from example 1 in that Fe2O3: the mass ratio of LMNCO to Mo is 13 percent, and FeCl3·6H2The amount of O (99.0%) added was 1.318g, and the positive electrode material prepared was designated LMNCO-Mo-13F.
Comparative example
This comparative example differs from example 1 in that NaOH solution was used as the precipitant and Na was not contained in the precipitant2MoO4Thereby obtaining a lithium-rich manganese-based positive electrode material (Li) containing no molybdenum element1.2Mn0.56Ni0.16Co0.08O2) And is recorded as LMNCO.
Examples of effects
SEM test
The morphology of the cathode material prepared in example 1 was observed under a scanning electron microscope, and the result is shown in fig. 1.
As can be seen from fig. 1, the positive active material prepared in example 1 had a spherical particle morphology, a particle diameter of about 10 to 15m, and no significant edge angle.
In addition, the characterization results of the scanning electron microscope of other embodiments are consistent with the results of embodiment 1, the surface of the material is smooth, and the crystallization is complete. The particle size is slightly increased with the increase of the coating ratio, and can reach about 17m at most.
XRD test results
XRD analysis and test are carried out on the lithium-rich manganese-based positive electrode materials prepared in the example 1 and the comparative example, and the specific result is shown in figure 2.
As can be seen from FIG. 2, the positive electrode material shows sharp diffraction peaks, which indicates that both samples have higher crystallinity, and meanwhile, the doped and coated lithium-rich manganese-based positive electrode material still has a good layered structure, and the inherent properties of the raw material are maintained.
The XRD detection results of other examples are the same as the detection results of example 1, all of which show that different coating ratios do not change the inherent structure of the lithium-rich manganese-based layered lithium ion battery positive electrode material, and the inherent properties thereof are maintained.
3. Electrochemical Performance test
The positive electrode materials obtained in example 5, example 6 and comparative example were respectively combined into button cells of model CR2032, and electrochemical performance tests were performed, and the results are shown in fig. 3 to 5.
The manufacturing steps of the CR2032 button cell are as follows:
(1) mixing a lithium-rich manganese-based positive electrode material, polyvinylidene fluoride and Super P in an agate ball-milling tank according to the mass ratio of 8:1:1, adding a proper amount of N-methylpyrrolidone into the ball-milling tank, and grinding the mixture to obtain uniform viscous slurry to obtain slurry; uniformly coating the slurry on an aluminum foil by using a coating machine, wherein the coating thickness is 150 mu m, and preparing a smear; the smears were dried in a drying cabinet at 70 ℃ for 5h and then dried at 120 ℃ under vacuum for 12 h. And then, the round positive plate with the diameter of 12mm is prepared after the round positive plate is compacted and shaped by a roller press.
(2) The lithium metal sheet is taken as a negative electrode, the polypropylene-polyethylene-polypropylene three-layer composite membrane is taken as a diaphragm, and 1mol/L LiPF6And (EC + DMC + DEC) is electrolyte, and the electrolyte is assembled into a CR2032 type button cell in a glove box filled with argon.
The battery is subjected to constant-current charge and discharge test by adopting a Xinwei high-performance battery detection system, and the charge and discharge voltage range is 2.0V-4.8V. The electrochemical performance test temperature was 25 ℃.
As a result:
as can be seen from FIG. 3, Fe is doped by Mo2O3The coated lithium-rich manganese-based positive electrode material has higher first discharge specific capacity. Other examples all showed higher initial capacity than comparative examples, with example 5 being the most effective modification.
And fig. 4 and 5 are the results of cycle performance and rate performance test at 25 ℃ of the button cell prepared by using the positive electrode material of example 5 and the comparative example. In fig. 4, the cell was activated for 3 cycles at 0.1C, followed by 100 cycles at 0.5C rate. The comparison shows that the discharge specific capacity of the anode material after double-effect modification is obviously higher than that of the unmodified LMNCO. And the discharge specific capacity of the LMNCO shows a rapid attenuation trend along with the increase of the cycle times, after 100 cycles, the discharge specific capacity of the LMNCO is attenuated from 208.3 mA.h/g to 177.2 mA.h/g, and the capacity retention rate is 85.0%. Under the same cycle number, the specific discharge capacity of LMNCO-Mo-5FThe capacity retention rate reaches 93.8 percent by attenuating from 238.4 mA.h/g to 223.5 mA.h/g, and other embodiments are improved mainly because of the nanometer Fe2O3The coating can inhibit the dissolution of the active material in the electrolyte, improve the structural stability of the anode material and further improve the cycle life.
As can be seen from fig. 5, when the multiplying power is gradually increased, the specific discharge capacity of the cathode material modified by the doping and coating combination is significantly higher than that of the unmodified cathode material. In addition, when the multiplying power is returned to 0.1C from 10C, the discharge specific capacity of the modified cathode material is still remarkably higher than that of the unmodified cathode material, and the modified cathode material can be almost recovered to the original capacity. Therefore, the doping and coating combined modification provided by the application is beneficial to improving the rate capability of the anode material. Due to the doping of molybdenum element, lattice parameters are enlarged, oxygen release is weakened, and therefore structural stability is improved, meanwhile, the corrosion effect of electrolyte on the anode material is reduced through the iron oxide coating layer, a compact and stable SEI film is formed on the surface of the material, and the surface stability of the anode material is improved. The two modification means are combined, so that the electrochemical performance of the lithium-rich manganese-based positive electrode material can be obviously improved.
In summary, the present application provides a Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based cathode material comprises the steps of preparing molybdenum-containing manganese-based hydroxide precipitate by a coprecipitation method, washing to obtain a precursor, mixing the precursor with lithium hydroxide, calcining, and preparing the precursor and ferric chloride together to obtain the cathode material with a pure-phase layered crystal structure. The anode material is doped with molybdenum element, the doped molybdenum element can enter the crystal lattice to replace the main element manganese under the high temperature condition, and the radius of the molybdenum ion is larger than that of the manganese ion, so that the crystal lattice parameter can be enlarged by replacing the manganese element with the molybdenum element, the effect of improving the speed performance is achieved, the oxygen release can be weakened, the crystal structure is stable, and the discharge specific capacity and the cycle performance are effectively improved. The positive electrode material can effectively inhibit the corrosion of the electrolyte to the positive electrode material by coating compact ferric oxide on the surface of the positive electrode material, so that the positive electrode material has good stability, high first coulombic efficiency and high first coulombic efficiency, and simultaneouslyThe cycle performance and the rate capability of the anode material can be further improved. Compared with the prior art, the cathode material combines molybdenum doping and ferric oxide modification, and after double-effect modification, the cycle stability, rate capability, first discharge specific capacity and other electrochemical properties of the lithium-rich manganese-based cathode material are improved.
The embodiments described above are some, not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims (10)

1. Mo-doped Fe2O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized by comprising the following steps of:
mixing NiCl2、CoCl2And MnCl2Dissolving in water to obtain a first mixed solution; mixing NaOH and Na2MoO4Mixing to obtain precipitant; mixing the mixed solution I, a precipitator and ammonia water under the protection of argon to prepare a mixed solution II, and stirring the mixed solution II to perform solid-liquid separation to prepare molybdenum-containing manganese-based hydroxide precipitate; washing the molybdenum-manganese containing hydroxide precipitate, and drying at the temperature of 75-85 ℃ for 11-13 h to prepare a precursor;
mixing the precursor with LiOH, mixing with a dispersant I, sequentially grinding and drying, calcining for 4.5-5.5 h at 490-510 ℃, heating to 845-855 ℃, calcining for 23-25 h, and cooling to obtain the Mo-doped lithium-rich manganese-based material;
dispersing the Mo-doped lithium-rich manganese-based material and a dispersant in water, and adding FeCl3After stirring for 1.8h-2.2h, adding alkali for precipitation, and stirring for 4.8h-5.2h to obtain a material; washing the material, and drying for 4.5-5.5 h at 55-65 ℃ to obtain a prefabricated product; the preform was then placed in a tube furnace at 490 deg.CFiring at the temperature of-510 ℃ for 2.8h-3.2h to prepare the cathode material.
2. Mo-doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that NiCl2、CoCl2And MnCl2The molar ratio of (6.5-7.5) to (2: 1).
3. Mo doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that the pH value of the mixed solution II is 9-11.
4. Mo doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that the stirring speed of the mixed solution II is 290-310 rpm, and the stirring temperature is 65 +/-3 ℃.
5. Mo-doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that the precursor and LiOH are mixed by n(Ni+Co+Mn+Mo)/nLiMixing at a ratio of 1: 1.55.
6. Mo doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that the first dispersing agent is absolute ethyl alcohol.
7. Mo-doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that the second dispersing agent is polyvinylpyrrolidone.
8. Mo-doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based cathode material is characterized in that in the process of adding alkali for precipitation, 0.45-0.55 mol/L NaOH solution is added dropwise to form a precipitate.
9. Mo-doped Fe according to claim 12O3The preparation method of the coated lithium-rich manganese-based positive electrode material is characterized in that the mixed solution II is stirred and then subjected to solid-liquid separation in a vacuum filtration mode to prepare molybdenum-manganese-containing hydroxide precipitate.
10. Mo-doped Fe2O3The coated lithium-rich manganese-based cathode material is characterized in that Mo is doped with Fe2O3The coated lithium-rich manganese-based cathode material is prepared by doping Mo of any one of claims 1-9 with Fe2O3The coated lithium-rich manganese-based positive electrode material is prepared by the preparation method.
CN202210482585.XA 2022-05-05 2022-05-05 Mo-doped Fe2O3Coated lithium-rich manganese-based positive electrode material and preparation method thereof Withdrawn CN114649522A (en)

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