CN114784261B - Lithium battery positive electrode material and preparation method thereof - Google Patents
Lithium battery positive electrode material and preparation method thereof Download PDFInfo
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- CN114784261B CN114784261B CN202210701411.8A CN202210701411A CN114784261B CN 114784261 B CN114784261 B CN 114784261B CN 202210701411 A CN202210701411 A CN 202210701411A CN 114784261 B CN114784261 B CN 114784261B
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- 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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- 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
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- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/502—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese for non-aqueous cells
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a lithium battery positive electrode material and a preparation method thereof, and belongs to the technical field of lithium battery positive electrode materials. The method comprises the following steps: mixing the solid manganese dioxide with an active material for preparing the lithium battery positive electrode material in a closed container at the temperature lower than-10 ℃, subliming the solid manganese dioxide into gas, subliming the gas into solid manganese dioxide, and continuously mixing. The method can realize uniform coating of manganese dioxide on the surface and interface of the lithium battery material, has high coating firmness and strength, and is beneficial to improving the cycle performance of the material and the contact stability of the lithium battery anode material and electrolyte. The lithium battery positive electrode material prepared by the method has good high-temperature cycle performance.
Description
Technical Field
The invention relates to the technical field of lithium battery positive electrode materials, in particular to a lithium battery positive electrode material and a preparation method thereof.
Background
Besides being determined by the nature of the constituent elements and the structure of the lithium battery material, the surface interface of the lithium battery material has a crucial influence on the electrochemical performance of the lithium battery material. Such as LiMn 2 O 4 Although the material has the advantages of low cost, stable structure, good low-temperature performance and the like, the problem of attenuation of high-temperature cycle performance is actually caused by continuous side reaction between the surface of the material and electrolyte. The LiMn can be reduced by the measures of surface spheroidization, large single crystallization, surface coating and the like 2 O 4 The direct contact area of the material surface and the electrolyte realizes LiMn 2 O 4 Commercial application of the material.
At present, the method for improving the surface interface of the lithium battery material through coating mainly comprises two strategies of physical coating and chemical coating, and in consideration of practical process feasibility, the method mainly takes the mode of 'mechanically fusing/mixing and thermally treating' an active material and nano powder coating as a main mode, and the coating has the characteristic of simple process, but the actual coating effect on the surface interface of the material is not ideal.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a preparation method of a lithium battery positive electrode material, which can simultaneously have a good coating effect on a material surface interface.
The second purpose of the invention is to provide a lithium battery positive electrode material prepared by the preparation method.
The application can be realized as follows:
in a first aspect, the present application provides a method for preparing a positive electrode material of a lithium battery, comprising the following steps: mixing the solid manganese dioxide with an active material for preparing the lithium battery positive electrode material in a closed container at the temperature lower than-10 ℃, subliming the solid manganese dioxide into gas, subliming the gas into solid manganese dioxide, and continuously mixing.
In an alternative embodiment, the active material includes at least one of a lithium manganate material, a lithium rich manganese material, and a ternary material.
In an alternative embodiment, the molar ratio of manganese dioxide solids to active material is 0.1 to 1: 100.
In an alternative embodiment, the mixing time is continued for 25-35 min.
In alternative embodiments, the manner in which the manganese dioxide solid is sublimated into a gas comprises adjusting the temperature within the closed vessel and/or adjusting the pressure of the closed vessel.
In an alternative embodiment, the pressure in the closed container is reduced to 0.01 to 0.08MPa when the pressure is adjusted.
In an alternative embodiment, the means for desublimating the manganese heptaoxide gas to a solid comprises adjusting the temperature within the closed vessel.
In an alternative embodiment, the temperature in the closed vessel is adjusted to 0 to 5 ℃.
In an alternative embodiment, the temperature within the closed container is adjusted to 0-5 ℃ under vibration conditions.
In an alternative embodiment, the amplitude is 1-3mm and the vibration frequency is 20-40 Hz.
In an alternative embodiment, after the manganese dioxide gas is desublimated into a solid and mixing is continued for 25-35min, the method further comprises: the temperature in the closed container is adjusted to 120 ℃ and 180 ℃ and the mixture is continuously mixed for 25-35 min.
In an alternative embodiment, the mixing process after temperature adjustment to 120-180 ℃ is carried out under shaking conditions.
In an alternative embodiment, the amplitude during mixing after temperature adjustment to 120-180 ℃ is 1-3mm and the vibration frequency is 20-40 Hz.
In an alternative embodiment, after the temperature is adjusted to 120-180 ℃ for mixing, the closed container is returned to normal pressure and cooled.
In an alternative embodiment, the method further comprises performing heat treatment at a temperature of not higher than 600 ℃ for not longer than 5h after cooling.
In an alternative embodiment, the heat treatment temperature is 300-.
In a second aspect, the present application provides a lithium battery positive electrode material prepared by the preparation method according to any one of the foregoing embodiments.
The beneficial effect of this application includes:
according to the method, manganese dioxide is sublimated into a gaseous state firstly in a sublimation and desublimation mode firstly, and is uniformly distributed in a closed container, so that the active material to be coated is covered and distributed in the atmosphere filled with the manganese dioxide, and under the condition, the manganese dioxide can be distributed on all surfaces of the active material to be coated (namely the surface of each position of the active material to be coated is exposed in the atmosphere filled with the gaseous manganese dioxide), and then is desublimated, so that the manganese dioxide and the surface of the active material to be coated are subjected to redox reaction, comprehensive and uniform chemical coating (good coating firmness and strength) of the surface and the interface of the material to be coated by a coating is realized, the oxidation state of transition metal on the surface of the active material is improved while coating, and the material performance (such as high-temperature cycle performance) is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention 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 SEM scanning electron micrograph of the surface of the clad material obtained in example 1 at 10000 times;
FIG. 2 is a SEM scanning electron microscope image of 10000 times the surface of the coating material obtained in example 2;
FIG. 3 is an SEM scanning electron micrograph of the surface of the clad material obtained in example 3 at 10000 times;
FIG. 4 is a SEM scanning electron micrograph of the surface of the clad material obtained in comparative example 1 at 10000 times;
FIG. 5 is a SEM scanning electron micrograph of the surface of the clad material obtained in comparative example 2 at 10000 times;
FIG. 6 is a SEM scanning electron micrograph of the surface of the clad material obtained in comparative example 3 at 10000 times;
FIG. 7 is a SEM scanning electron micrograph of the surface of the clad material obtained in comparative example 4 at 10000 times;
FIG. 8 is a SEM scanning electron micrograph of the surface of the clad material obtained in comparative example 5 at 10000 times;
FIG. 9 is an SEM scanning electron micrograph of a surface of the clad material obtained in comparative example 6 at 10000 times;
FIG. 10 is a SEM scanning electron micrograph of the surface of the clad material obtained in comparative example 7 at 10000 times;
FIG. 11 is a surface EDX spectrum of the clad material obtained in example 2;
FIG. 12 is an EDX spectrum of the surface of the clad material obtained in example 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of 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 conventional products which are not indicated by manufacturers and are commercially available.
The lithium battery positive electrode material and the preparation method thereof provided by the present application are specifically described below.
The application provides a preparation method of a lithium battery positive electrode material, which comprises the following steps: mixing the solid manganese dioxide with an active material for preparing the lithium battery positive electrode material in a closed container at the temperature lower than-10 ℃, subliming the solid manganese dioxide into gas, subliming the gas into solid manganese dioxide, and continuously mixing for 25-35 min.
The active material may include, for example and without limitation, at least one of a lithium manganate material, a lithium-rich manganese material, and a ternary material, among others.
For reference, the molecular formula of the lithium manganate material may be LiM x Mn 2-x O 4 (x is more than or equal to 0 and less than or equal to 0.6, M represents any metal element), and the molecular formula of the lithium-rich manganese material can be xLi 2 MnO 3 ·(1-x)LiMO 2 (wherein x is more than or equal to 0 and less than or equal to 1, and M = one or more of Ni, Co, Fe and Cr), the molecular formula of the ternary material can be LiNi x Co y Mn 1-x-y O 2 (0≤x+y≤1)。
The molar ratio of manganous oxide solid to active material may be 0.1-1:100, such as 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, or 1:100, and may also be any other value within the range of 0.1-1: 100.
If the amount of the manganese dioxide solid is too small, the effect of effectively coating the surface interface of the active material cannot be achieved; if the amount of the manganese dioxide solid is too large, a thick manganese-rich layer is formed on the surface of the active material, so that the lithium ions in the original active material are prevented from entering and exiting.
The mixing temperature of the manganous oxide solid and the active material can be-11 ℃, 12 ℃, 15 ℃, 18 ℃ or 20 ℃ and the like.
Under the above conditions, manganese pentoxide was mixed in solid form with the active material. It should be noted that, if the manganese heptaoxide solid and the active material are directly coated in a mixed manner, the manganese heptaoxide solid and the active material are combined by physical adsorption force, and actually, the manganese heptaoxide is contacted with points, and under the condition that the molar ratio is 0.1-1:100, the manganese heptaoxide can hardly coat all the surfaces of the active material completely and uniformly. If manganese pentoxide is mixed in liquid form with the active material, the rate of its permeability to the surface of the material is not fast enough, which also tends to result in non-uniform coating.
Based on the above, the inventor creatively proposes that manganese dioxide is firstly sublimated into a gaseous state and uniformly distributed in a closed container in a sublimation and desublimation mode, so that the active material to be coated is covered and distributed in the atmosphere filled with the manganese dioxide, under the condition, the manganese dioxide can be distributed on all surfaces of the active material to be coated (namely, the surface of each position of the active material to be coated is exposed to the atmosphere filled with the gaseous manganese dioxide), and then desublimation is carried out, so that the manganese dioxide and the surface of the active material to be coated are subjected to chemical action, and comprehensive and uniform coating (chemical coating) of the surface and the interface of the material to be coated is realized.
As a reference, the manner in which the manganese dioxide solid is sublimated into a gas includes adjusting the temperature within the closed vessel and/or adjusting the pressure of the closed vessel.
In some alternative embodiments, the manganese dioxide solid can be sublimated into gas by sublimation under reduced pressure, for example, the pressure in the closed container can be reduced to 0.01-0.08 MPa.
Specifically, the pressure in the sealed container after the pressure reduction may be 0.01MPa, 0.02MPa, 0.03MPa, 0.04MPa, 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, or 0.09MPa, or any other value within the range of 0.01 to 0.08 MPa.
Similarly, the means for desublimating the manganese heptaoxide gas to a solid comprises adjusting the temperature within the closed vessel. In some alternative embodiments, the temperature in the closed vessel may be adjusted to 0-5 ℃ when the temperature is adjusted.
Specifically, the adjusted temperature may be any temperature in the range of-10 ℃ (not including) to 5.9 ℃ (not including), such as 0 ℃, 0.5 ℃, 1 ℃, 1.5 ℃, 2 ℃, 2.5 ℃, 3 ℃, 3.5 ℃, 4 ℃, 4.5 ℃ or 5 ℃.
And adjusting the temperature in the closed container to 0-5 ℃ under the vibration condition, and maintaining the vibration condition to mix the desublimated manganese heptaoxide solid with the active material to be coated.
The active material to be coated can be in a loose suspension state in the closed container and the position of the active material is constantly changed by adjusting the temperature and mixing the materials under the vibration condition, namely, the active material positioned below the closed container at a certain moment is changed to be positioned above the closed container at the next moment after being vibrated, or the active material positioned on the left side of the closed container at a certain moment is changed to be positioned on the right side of the closed container at the next moment after being vibrated, or the active material positioned on the front side of the closed container at a certain moment is changed to be positioned on the rear side of the closed container at the next moment after being vibrated. Therefore, active materials to be coated at all positions in the closed container can be fully contacted with the manganese dioxide gas, gaps in the coated active material body can be contacted with the manganese dioxide gas, and uniform mixing effect can be achieved after the active materials are desublimated into solids.
The amplitude of the vibration process may be, for example, 1-3mm, such as 1mm, 1.5mm, 2mm, 2.5mm or 3mm, and may be any other value within the range of 1-3 mm.
The vibration frequency may be 20-40Hz, such as 20Hz, 25Hz, 30Hz, 35Hz, or 40Hz, or any other value within the range of 20-40 Hz.
At the above amplitudes and frequencies, efficient bonding of the manganese heptaoxide solid to the active material is facilitated. If the amplitude is too large, the aggregation form of the active material is easily changed, and fine powder harmful to the electrical property is generated; if the amplitude is too small, insufficient contact between the manganese dioxide and the material is easily caused; similarly, if the vibration frequency is too high, the aggregation form of the active material is easily changed, and fine powder harmful to the electrical property is generated; if the vibration frequency is too low, the working time tends to be prolonged.
The mixing time of the manganese dioxide gas which is desublimated into solid and then continuously mixed with the anode material to be coated can be 25min, 28min, 30min, 32min or 35min and the like, and can also be any value within the range of 25-35 min.
Under the mixing range, the manganese dioxide gas which is desublimated into solid can be effectively and uniformly coated on all surfaces and interfaces of the positive electrode material to be coated.
In some embodiments, the temperature may be adjusted to 5 ℃ under the conditions of an amplitude of 1 to 3mm and a vibration frequency of 20 to 40Hz after the depressurization, and the manganese heptaoxide solid may be mixed with the active material for 30min under the vibration conditions.
Further, after the manganese dioxide gas is desublimated into a solid and continuously mixed for 25-35min, the method also comprises the following steps: the temperature in the closed container is adjusted to 120 ℃ and 180 ℃ and the mixture is continuously mixed for 25-35 min.
The temperature after the continuous adjustment may be, for example, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃ or 180 ℃, or may be any other value within the range of 120 ℃ and 180 ℃.
The mixing time after the temperature is continuously adjusted can be 25min, 28min, 30min, 32min, 35min or the like, and can also be any other value within the range of 25-35 min.
The residual and uncoated manganese dioxide can be decomposed by continuously mixing at the temperature of 120-180 ℃ for 25-35min, and finally the purpose of no residue is achieved.
Preferably, the treatment process after the temperature is raised to 120-180 ℃ is also performed under vibration.
In reference, the amplitude during the treatment process after the temperature is raised to 120-180 ℃ can also be 1-3mm, and the vibration frequency can also be 20-40 Hz.
In some embodiments, after the treatment at 0-5 deg.C for 25-35min, the temperature is adjusted to 150 deg.C and the treatment is carried out at amplitude of 1-3mm and vibration frequency of 20-40Hz for 30 min.
In an alternative embodiment, after the temperature is raised to 120-180 ℃ for treatment for 25-35min, the closed container is returned to normal pressure and cooled.
Accordingly, Mn having a strong oxidizing property is obtained by the above method 2 O 7 And the surface of the active material is subjected to redox reaction, so that the chemical coating of a substrate by a coating material is realized (the coating is firm and the coating strength is good), the oxidation state of transition metal on the surface of the active material is improved while the coating is carried out, and the material performance is improved.
Specifically, in the above process, Mn 2 O 7 Can convert transition metal (Mn) in low valence state 2+ /Mn 3+ /Ni 2+ Etc.) to a higher valence state (Mn) 4+ / Ni 3+ Etc.) which are themselves reduced to MnO 2 And MnO of 2 The manganese-rich composite material is also an active component of the lithium battery material, no additional impurity is introduced, and the finally formed high-valence manganese-rich layer with a certain thickness can effectively improve the contact stability of the material and electrolyte.
For example, when the method is used for coating lithium manganate material, the method provided by the application can eliminate Mn on the surface of lithium manganate 3+ The problem of high-temperature manganese dissolution of lithium manganate is reduced, and the high-temperature cycle performance of the material is improved.
When the material is used for coating ternary materials (particularly high-nickel materials), MnO can be formed on the surface of the material 2 Layer for effectively isolating a large amount of Ni appearing on the surface of the ternary material at the final stage of charging 4+ Resulting in side reactions with the electrolyte, enhancing cycle performance.
When used for coating a lithium-rich manganese-based material, MnO may be formed on the surface thereof 2 And the layer prevents the loss of active oxygen of the lithium-rich manganese material during the first high-voltage charging activation, and enhances the cycle performance.
Further, the method can also comprise the step of carrying out heat treatment for not more than 5 hours at the temperature of not more than 600 ℃ after cooling.
The temperature of the heat treatment can be 300-600 deg.C, such as 300 deg.C, 350 deg.C, 400 deg.C, 450 deg.C, 500 deg.C, 550 deg.C or 600 deg.C, and can be any other value within the range of 300-600 deg.C. In addition, it may be carried out at 200 ℃ or other temperatures within the above-mentioned range.
The time of the heat treatment may be, for example, 2 to 5 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours, and may be any other value within the range of 2 to 5 hours. In addition, 1h or other time periods meeting the above range may also be processed.
Through the heat treatment process, the stability of the product can be further improved.
Correspondingly, the application also provides a lithium battery positive electrode material prepared by the preparation method.
The prepared lithium battery positive electrode material has a good coating effect and is beneficial to improving the cycle performance.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a lithium battery positive electrode material, and a preparation method thereof comprises the following steps:
mixing manganese heptaoxide solid and lithium manganate material (molecular formula is LiMn) in a closed container at-11 DEG C 2 O 4 ) Mixing at a molar ratio of 0.5:100, then sublimating the manganese dioxide solid into gas under reduced pressure by reducing the pressure in the closed vessel to 0.05MPa, adjusting the temperature in the closed vessel to 5 ℃ under vibration conditions (amplitude of 2mm, vibration frequency of 30 Hz) to desublimate the manganese dioxide gas into solid and continuing mixing for 30 min.
Subsequently, the temperature in the closed vessel was adjusted to 150 ℃ under vibration conditions (amplitude of 2mm, vibration frequency of 30 Hz) and mixing was continued for 30 min.
Stopping vibration, introducing oxygen to restore the pressure of the container to normal pressure, cooling to room temperature, and taking out the target product.
Subsequently, the mixture was further heat-treated at 500 ℃ for 5 hours.
Example 2
The embodiment provides a lithium battery cathode material, and a preparation method thereof is as follows:
in a closed container at-8 ℃, manganese dioxide solid and lithium-rich manganese material (molecular formula is Li) 1.2 Ni 0.32 Mn 0.48 O 2 ) Mixing at a molar ratio of 0.1:100, then sublimating the manganese dioxide solid into gas under reduced pressure by reducing the pressure in the closed vessel to 0.01MPa, adjusting the temperature in the closed vessel to 0 ℃ under vibration conditions (amplitude of 1mm, vibration frequency of 20 Hz) to desublimate the manganese dioxide gas into solid, and continuing mixing for 35 min.
Subsequently, the temperature in the closed vessel was adjusted to 120 ℃ under vibration conditions (amplitude of 1mm, vibration frequency of 20 Hz) and mixing was continued for 35 min.
Stopping vibration, introducing oxygen to restore the pressure of the container to normal pressure, cooling to room temperature, and taking out the target product.
Subsequently, the mixture was further heat-treated at 300 ℃ for 4 hours.
Example 3
The embodiment provides a lithium battery cathode material, and a preparation method thereof is as follows:
in a closed container at the temperature of minus 5 ℃, manganese dioxide solid and ternary material (molecular formula is LiNi) 0.83 Co 0.11 Mn 0.06 O 2 ) Mixing at a molar ratio of 1:100, then sublimating the manganous oxide solid into gas under reduced pressure by reducing the pressure in the closed container to 0.08MPa, adjusting the temperature in the closed container to 2 ℃ under vibration conditions (amplitude of 3mm and vibration frequency of 40 Hz) to desublimate the manganous oxide gas into solid, and continuing mixing for 25 min.
Subsequently, the temperature in the closed vessel was adjusted to 180 ℃ under vibration conditions (amplitude of 3mm, vibration frequency of 40 Hz), and mixing was continued for 25 min.
Stopping vibrating, introducing oxygen to restore the pressure of the container to normal pressure, cooling to room temperature, and taking out the target product.
Subsequently, the mixture was further heat-treated at 600 ℃ for 3 hours.
Comparative example 1
The comparative example provides a lithium battery positive electrode material, and the preparation method comprises the following steps:
directly mixing manganese dioxide solid with lithium manganate material (molecular formula is LiMn) 2 O 4 ) Mixing at a molar ratio of 0.5:100 for 30min, and then mixingAdjusting the temperature in the sealed container to 150 ℃ under vibration conditions (amplitude of 2mm and vibration frequency of 30 Hz), continuously mixing for 30min, and then performing heat treatment for 5h at 500 ℃.
That is, the comparative example was a case where solid manganese heptaoxide was directly mixed with a lithium manganate material without sublimation first and then sublimation.
Comparative example 2
The comparative example provides a lithium battery positive electrode material, and the preparation method comprises the following steps:
mixing manganese dioxide solution with lithium manganate material (molecular formula is LiMn) at 25 deg.C 2 O 4 ) Mixing at a molar ratio of 0.5:100 for 30min, adjusting the temperature in the sealed container to 150 deg.C under vibration condition (amplitude of 2mm and vibration frequency of 30 Hz), mixing for 30min, and heat treating at 500 deg.C for 5 h.
That is, the comparative example was a method in which a manganese heptaoxide liquid was directly mixed with a lithium manganate material.
Comparative example 3
The comparative example provides a lithium battery positive electrode material, and the preparation method comprises the following steps:
directly mixing manganese heptaoxide solid with lithium-rich manganese material (molecular formula is Li) 1.2 Ni 0.32 Mn 0.48 O 2 ) Mixing at a molar ratio of 0.1:100 for 35min, adjusting the temperature in the sealed container to 120 deg.C under vibration (amplitude of 1mm and vibration frequency of 20 Hz), mixing for 35min, and heat treating at 300 deg.C for 4 h.
That is, the comparative example was a direct blend of manganese heptaoxide solids and lithium-rich manganese materials without the steps of sublimation followed by desublimation.
Comparative example 4
The comparative example provides a lithium battery positive electrode material, and the preparation method comprises the following steps:
mixing manganese heptaoxide liquid with lithium-rich manganese material (molecular formula is Li) at 25 deg.C 1.2 Ni 0.32 Mn 0.48 O 2 ) Mixing at a molar ratio of 0.1:100 for 35min, and then adjusting the temperature in the sealed container to 120 deg.C under vibration conditions (amplitude of 1mm and vibration frequency of 20 Hz)Mixing for 35min, and heat treating at 300 deg.C for 4 hr.
That is, the comparative example was a direct mix of manganese heptaoxide liquid and lithium-rich manganese material.
Comparative example 5
The comparative example provides a lithium battery positive electrode material, and the preparation method comprises the following steps:
directly mixing manganese dioxide solid with ternary material (molecular formula is LiNi) 0.83 Co 0.11 Mn 0.06 O 2 ) Mixing at a molar ratio of 1:100 for 25min, adjusting the temperature in the sealed container to 180 deg.C under vibration condition (amplitude of 3mm and vibration frequency of 40 Hz), mixing for 25min, and heat treating at 600 deg.C for 3 h.
That is, the comparative example was a direct mixture of manganese heptaoxide solids and ternary materials without the steps of sublimation followed by desublimation.
Comparative example 6
The comparative example provides a lithium battery positive electrode material, and the preparation method comprises the following steps:
at 25 deg.C, mixing manganese dioxide solution with ternary material (molecular formula is LiNi) 0.83 Co 0.11 Mn 0.06 O 2 ) Mixing at a molar ratio of 1:100 for 25min, adjusting the temperature in the sealed container to 180 deg.C under vibration condition (amplitude of 3mm and vibration frequency of 40 Hz), mixing for 25min, and heat treating at 600 deg.C for 3 h.
That is, the comparative example was a direct blend of manganese heptaoxide liquid and ternary material.
Comparative example 7
The comparative example differs from example 1 in that: the mixing step in the preparation process is not carried out under vibration conditions.
Test examples
The lithium battery positive electrode materials prepared in the examples 1 to 3 and the comparative examples 1 to 7 are used as samples 1 to 10 to be tested, and coating uniformity detection and high-temperature cycle performance test are carried out.
Wherein, the coating uniformity detection is carried out by adopting a scanning electron microscope and EDX method.
The high-temperature cycle performance test is carried out according to a conventional 2032 power-off test method, and the test temperature is 45 ℃.
The results of the coating uniformity are shown in fig. 1 to 12 and tables 1 and 2, wherein the abscissa of fig. 11 and 12 represents energy, specifically, energy of X-ray, and the unit is kev; the ordinate represents the number of counts, in particular X-rays, in cps, and the "K" after the number on the ordinate represents 10 3 。
Table 1 EDX spectroscopy results corresponding to example 2
Table 2 EDX spectroscopy results corresponding to example 3
From the above coating uniformity test and EDX results, it can be seen that: the surface coating of the lithium battery positive electrode material prepared in the embodiment 1 is obviously more uniform than that of the positive electrode material prepared in the comparative example 1 and the positive electrode material prepared in the comparative example 2, the surface coating of the lithium battery positive electrode material prepared in the embodiment 2 is obviously more uniform than that of the positive electrode material prepared in the comparative example 3 and the positive electrode material prepared in the comparative example 4, and the surface coating of the lithium battery positive electrode material prepared in the embodiment 3 is obviously more uniform than that of the positive electrode material prepared in the comparative example 5 and the positive electrode material prepared in the comparative example 6; in addition, the surface coating of the lithium battery positive electrode material prepared in example 1 is obviously more uniform than that of comparative example 7.
② the test result of the high temperature cycle performance is shown in table 3.
TABLE 3 high temperature cycling Performance test results
As can be seen from table 3, the lithium battery positive electrode material prepared in example 1 has a higher high-temperature cycle performance than the lithium battery positive electrode materials obtained in comparative examples 1 and 2, the lithium battery positive electrode material prepared in example 2 has a higher high-temperature cycle performance than the lithium battery positive electrode materials obtained in comparative examples 3 and 4, and the lithium battery positive electrode material prepared in example 3 has a higher high-temperature cycle performance than the lithium battery positive electrode materials obtained in comparative examples 5 and 6; in addition, the lithium battery positive electrode material prepared in example 1 has a higher high-temperature cycle performance than the lithium battery positive electrode material prepared in comparative example 7.
In summary, in the present application, manganese dioxide is sublimated into a gaseous state and uniformly distributed in the closed container in a sublimation and desublimation manner, so that the active material to be coated is covered and distributed in the atmosphere filled with manganese dioxide, under such a condition, manganese dioxide gas can be distributed on all surfaces of the active material to be coated (i.e., the surface of each position of the active material to be coated is exposed to the atmosphere filled with gaseous manganese dioxide), and then desublimation is performed, so that a redox reaction is performed between the manganese dioxide gas and the surface of the active material to be coated, thereby achieving comprehensive and uniform chemical coating (good coating firmness and strength) of the coating on the surface and interface of the material to be coated by the coating material, and improving the oxidation state of the transition metal on the surface of the active material while coating, and improving the material performance.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the lithium battery positive electrode material is characterized by comprising the following steps of: mixing a manganous oxide solid with an active material for preparing a lithium battery positive electrode material in a closed container at the temperature lower than-10 ℃, subliming the manganous oxide solid into gas, subliming the manganous oxide gas into a solid, and continuously mixing;
the active material comprises at least one of a lithium manganate material, a lithium-rich manganese material and a ternary material;
the molar ratio of the manganese heptaoxide solid to the active material is 0.1-1: 100;
continuously mixing for 25-35 min;
the way of desublimating the manganese heptaoxide gas into a solid is as follows: adjusting the temperature in the closed container to 0-5 ℃ under the vibration condition; the amplitude is 1-3mm, and the vibration frequency is 20-40 Hz.
2. The method of claim 1, wherein subliming the manganese heptaoxide solid into a gas comprises adjusting a temperature within the closed vessel and/or adjusting a pressure of the closed vessel.
3. The production method according to claim 2, wherein the pressure in the closed vessel is reduced to 0.01 to 0.08MPa when the pressure is adjusted.
4. The method according to any one of claims 1 to 3, further comprising, after the manganese dioxide gas is desublimated to a solid and mixed for 25 to 35 minutes: the temperature in the closed container is adjusted to be 180 ℃ for continuous mixing for 25-35 min.
5. The method as claimed in claim 4, wherein the mixing process after the temperature adjustment to 120-180 ℃ is carried out under vibration.
6. The preparation method as claimed in claim 5, wherein the amplitude in the mixing process after the temperature is adjusted to 120-180 ℃ is 1-3mm and the vibration frequency is 20-40 Hz.
7. The preparation method as claimed in claim 4, wherein the temperature is adjusted to 120 ℃ + 180 ℃ and the mixture is cooled after the closed container is returned to normal pressure.
8. The method of claim 7, further comprising performing a heat treatment at a temperature of not higher than 600 ℃ for not longer than 5 hours after cooling.
9. The method as claimed in claim 8, wherein the heat treatment temperature is 300-600 ℃.
10. A lithium battery positive electrode material, characterized by being produced by the production method according to any one of claims 1 to 9.
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