CN108417830B - Lithium nickel manganese oxide positive electrode material and preparation method thereof - Google Patents
Lithium nickel manganese oxide positive electrode material and preparation method thereof Download PDFInfo
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- CN108417830B CN108417830B CN201810234855.9A CN201810234855A CN108417830B CN 108417830 B CN108417830 B CN 108417830B CN 201810234855 A CN201810234855 A CN 201810234855A CN 108417830 B CN108417830 B CN 108417830B
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- H01M4/00—Electrodes
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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
- H01M4/505—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
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- 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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Abstract
The invention provides a lithium nickel manganese oxide positive electrode material which is a micron rod assembled by lithium nickel manganese oxide nano particles, wherein the average particle size of the lithium nickel manganese oxide nano particles is 150-250 nm, the average diameter of the micron rod is 1.5-2.5 microns, and the average length of the micron rod is 6-12 microns. The invention provides a micron-nano assembled hierarchical structure, namely a hierarchical structure formed by combining nano particles and a micron rod structure, wherein the nano particles are beneficial to rapid insertion and extraction of lithium ions, the micron rod structure is a main body structure, the thermodynamic stability is excellent, and the specific capacity and the cycling stability of a lithium nickel manganese oxide positive electrode material are improved by combining the nano particles and the micron rod structure.
Description
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a lithium nickel manganese oxide anode material and a preparation method thereof.
Background
The increasing exhaustion of fossil energy has intensified the research of human beings on traditional energy substitute products. Lithium Ion Batteries (LIBs) are a novel energy source with the outstanding advantages of high energy density, long cycle life, small environmental pollution and the like, and have wide application prospects in various fields of mobile communication equipment (such as mobile phones), electric vehicles, hybrid vehicles and the like. Currently, the positive electrode material lithium cobaltate (LiCoO) is commercialized2) The battery has the defects of small capacity, poor rate performance and poor cycle stability, so that the market demand cannot be met. The cathode material with high capacity and high voltage becomes the research and development direction of the future high-performance lithium ion battery, and the application market of the cathode material is continuously expanding.
Lithium manganate (LiMn)2O4) The lithium manganate is a positive electrode material with a three-dimensional lithium ion channel, and compared with a lithium cobaltate positive electrode material, the lithium manganate has the advantages of low price, high potential, environmental friendliness, high safety performance and the like. And lithium nickel manganese oxide (LiNi)0.5Mn1.5O4) As a nickel substitute product of lithium manganate, the lithium manganate has the characteristics of high specific discharge capacity (theoretical specific capacity of 147mAh/g), and also has a 4.7V high-voltage discharge platform which is higher than the 4V voltage platform of lithium manganate by more than 15%.
However, when the lithium nickel manganese oxide is used as a positive electrode material, the electrochemical performance of the lithium nickel manganese oxide is often influenced by factors such as morphology, particle size, morphology and crystallinity to different degrees. In the prior art, the rate performance of the lithium nickel manganese oxide positive electrode material is improved by nanocrystallizing the lithium nickel manganese oxide, namely, the particle size is reduced to a nanometer size, so that the lithium manganese oxide positive electrode material is beneficial to the rapid transportation of lithium ions. However, due to the structural instability of the nanoparticles, the thermodynamic stability of the product is reduced and the interface energy is increased, so that the specific capacity and the cycling stability of the product are reduced.
Disclosure of Invention
The invention aims to provide a lithium nickel manganese oxide positive electrode material and a preparation method thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a lithium nickel manganese oxide positive electrode material which is a micron rod assembled by lithium nickel manganese oxide nano particles, wherein the average particle size of the lithium nickel manganese oxide nano particles is 150-250 nm, the average diameter of the micron rod is 1.5-2.5 microns, and the average length of the micron rod is 6-12 microns.
The invention also provides a preparation method of the lithium nickel manganese oxide positive electrode material, which comprises the following steps:
(1) dissolving nickel nitrate, manganese nitrate and glycine in water to obtain a raw material mixed solution;
(2) dropwise adding a strong base solution into the raw material mixed solution, and carrying out hydrothermal reaction to obtain a nickel-manganese precursor;
(3) and mixing the nickel-manganese precursor with lithium carbonate, and calcining to obtain the lithium nickel manganese oxide positive electrode material.
Preferably, the molar ratio of the nickel nitrate to the glycine is 1: 10-15.
Preferably, the strong alkaline solution is an aqueous solution of sodium hydroxide and/or potassium hydroxide.
Preferably, the concentration of alkali in the strong alkali solution is 5-8 mol/L; the ratio of the amount of the nickel nitrate to the volume of the strong alkali solution is 1mmol: 3-5 mL.
Preferably, the temperature of the hydrothermal reaction is 120-160 ℃, and the time of the hydrothermal reaction is 20-26 h.
Preferably, the calcination comprises a first calcination and a second calcination; the temperature of the first calcination is 300-400 ℃, and the time of the first calcination is 2-3 h; the temperature of the second calcination is 800-850 ℃, and the time of the second calcination is 6-8 h.
Preferably, the temperature rise rate of the temperature rise to the temperature required for the first calcination and the temperature rise to the temperature required for the second calcination is independently 100 to 150 ℃/h.
Preferably, the molar ratio of lithium atoms in the lithium carbonate to the nickel nitrate and the manganese nitrate is 1.03-1.06: 0.5: 1.5.
Preferably, the mixing in step (4) is grinding mixing.
The invention provides a lithium nickel manganese oxide positive electrode material which is a micron rod assembled by lithium nickel manganese oxide nano particles, wherein the average particle size of the lithium nickel manganese oxide nano particles is 150-250 nm, the average diameter of the micron rod is 1.5-2.5 microns, and the average length of the micron rod is 6-12 microns. The invention provides a micron-nano assembled hierarchical structure, namely a hierarchical structure formed by combining nano particles and a micron rod structure, wherein the nano particles are beneficial to rapid insertion and extraction of lithium ions, the micron rod structure is a main body structure, the thermodynamic stability is excellent, and the specific capacity and the cycling stability of a lithium nickel manganese oxide positive electrode material are improved by combining the nano particles and the micron rod structure.
Experimental results show that when the lithium nickel manganese oxide cathode material provided by the invention is used for preparing a lithium ion battery, the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, the battery can respectively provide reversible discharge specific capacities of 144 mAh/g, 140mAh/g, 131 mAh/g, 125 mAh/g, 118 mAh/g and 112mAh/g under the multiplying power of 1, 2, 5, 10, 15 and 20C, and the highest specific capacity is very close to the theoretical specific capacity of 147 mAh/g; and the battery is circularly charged and discharged for 200 times under the multiplying power of 1C, the specific capacity of the battery is still stabilized at 142mAh/g, the coulombic efficiency reaches 99.16%, and the battery has excellent circulating stability and multiplying power performance.
Drawings
FIG. 1 is a flow chart of a process for preparing a lithium nickel manganese oxide cathode material;
FIG. 2 is a scanning electron micrograph of a nickel-manganese precursor obtained in example 1, wherein a is a macroscopic scanning electron micrograph, and b is a macroscopic scanning electron micrograph;
FIG. 3 is a transmission electron micrograph of a nickel-manganese precursor obtained in example 1;
FIG. 4 is a scanning electron micrograph of a lithium nickel manganese oxide positive electrode material obtained in example 1, wherein a is a low-power scanning electron micrograph, and b is a high-power scanning electron micrograph;
FIG. 5 is a transmission electron micrograph of a lithium nickel manganese oxide positive electrode material obtained in example 1;
FIG. 6 is an XRD pattern of a lithium nickel manganese oxide positive electrode material obtained in example 1;
FIG. 7 is an infrared spectrum of a lithium nickel manganese oxide positive electrode material obtained in example 1;
FIG. 8 is a Raman spectrum of the lithium nickel manganese oxide positive electrode material obtained in example 1;
FIG. 9 is a cyclic voltammogram of a lithium ion battery prepared by using the lithium nickel manganese oxide cathode material obtained in example 1;
FIG. 10 is an AC impedance spectrum of a lithium ion battery using the lithium nickel manganese oxide positive electrode material obtained in example 1;
FIG. 11 is a charge-discharge curve of a lithium ion battery prepared by using the lithium nickel manganese oxide cathode material obtained in example 1;
FIG. 12 is a graph showing discharge rate performance of a lithium ion battery using the lithium nickel manganese oxide positive electrode material obtained in example 1;
FIG. 13 is a graph showing the cycle stability test of a lithium ion battery using the lithium nickel manganese oxide positive electrode material obtained in example 1.
Detailed Description
The invention provides a lithium nickel manganese oxide positive electrode material which is a micron rod assembled by lithium nickel manganese oxide nano particles, wherein the average particle size of the lithium nickel manganese oxide nano particles is 150-250 nm, the average diameter of the micron rod is 1.5-2.5 microns, and the average length of the micron rod is 6-12 microns.
In the invention, the average particle size of the lithium nickel manganese oxide nanoparticles is 150-250 nm, preferably 170-230 nm, and more preferably 190-210 nm.
In the present invention, the average diameter of the micro-rods is 1.5 to 2.5 μm, preferably 1.7 to 2.3 μm, and more preferably 1.9 to 2.1 μm.
In the invention, the average length of the micron rods is 6-12 μm, preferably 7-10 μm, and more preferably 7.5-9 μm.
The invention also provides a preparation method of the lithium nickel manganese oxide positive electrode material, which comprises the following steps:
(1) dissolving nickel nitrate, manganese nitrate and glycine in water to obtain a raw material mixed solution;
(2) dropwise adding a strong base solution into the raw material mixed solution, and carrying out hydrothermal reaction to obtain a nickel-manganese precursor;
(3) and mixing the nickel-manganese precursor with lithium carbonate, and calcining to obtain the lithium nickel manganese oxide positive electrode material.
The flow chart of the preparation method provided by the invention is shown in figure 1. Dripping strong alkaline solution into the raw material mixed solution, and mixing glycine with metal ions Ni2+And Mn2+Carrying out chelation to form a stable chelate, and carrying out hydrothermal reaction to obtain a rod-shaped nickel-manganese precursor with a smooth surface; uniformly mixing lithium carbonate and nickel manganese precursors, calcining, carrying out lithiation reaction, releasing carbon dioxide gas (shown as a gray shading part on the left side in fig. 1), and decomposing impurities to obtain a stable and pure lithium nickel manganese oxide positive electrode material, wherein the obtained lithium nickel manganese oxide positive electrode material is a micrometer rod with a hierarchical structure, namely a micrometer rod assembled by nano particles (shown as a structure in fig. 1).
The method comprises the steps of dissolving nickel nitrate, manganese nitrate and glycine in water to obtain a raw material mixed solution.
In the invention, the molar ratio of the nickel nitrate to the manganese nitrate is 1: 3.
In the invention, the molar ratio of the nickel nitrate to the glycine is preferably 1: 10-15, and more preferably 1: 12-13. In the present invention, the glycine acts as a chelating agent, chelating unstable Ni upon subsequent addition of a strong alkaline solution2+And Mn2 +Form a stabilizationThe chelate avoids heavy metal ions from forming hydroxide precipitates to form stable turbid liquid, guarantees the uniformity of subsequent hydrothermal reaction and the crystallinity of products, and avoids the aggregation and overlapping of the products.
After the raw material mixed solution is obtained, the strong base solution is dripped into the raw material mixed solution to obtain the suspension.
In the invention, the strong alkaline solution is added into the raw material mixed solution in a dropwise manner, so that Ni can be reduced2+And Mn2+The precipitation reaction rate with alkali is combined with the chelation of glycine to finally form a stable suspension.
In the present invention, the strong alkaline solution is preferably an aqueous solution of sodium hydroxide and/or potassium hydroxide; when the alkali solution is a mixture of the two, the ratio of sodium hydroxide and potassium hydroxide in the present invention is not particularly limited, and may be any ratio.
In the invention, the concentration of alkali in the strong alkali solution is preferably 5-8 mol/L, and more preferably 6-7 mol/L.
In the present invention, the ratio of the amount of the nickel nitrate to the volume of the alkali solution is preferably 1mmol:3 to 5mL, and more preferably 1mmol:3.5 to 4.5 mL.
In the invention, the dripping speed is preferably 2-4 s/droplet.
In the invention, the raw material mixed liquid is preferably in a stirring state in the dropping process; the rotation speed of the stirring is preferably 900-1100 rpm, and more preferably 950-1050 rpm.
After the dropwise addition is finished, the stirring is preferably continuously maintained for 0.5-2 hours to obtain a suspension.
In the present invention, the time for continuously maintaining the stirring is preferably 1 to 1.5 hours.
After obtaining the suspension, carrying out hydrothermal reaction on the suspension to obtain the nickel-manganese precursor. As shown in fig. 1, a rod-like nickel-manganese precursor was obtained after hydrothermal reaction.
In the invention, the temperature of the hydrothermal reaction is preferably 120-160 ℃, more preferably 130-150 ℃, and most preferably 135-145 ℃; the time of the hydrothermal reaction is preferably 20-26 h, and more preferably 22-24 h. In the invention, in the hydrothermal reaction process, water is used as a solvent and a pressure transfer medium to promote nickel manganese metal ions complexed by glycine to react with a sodium hydroxide solution, crystals are gradually nucleated, grown and crystallized and separated out along a one-dimensional direction, and finally, a nickel manganese precursor with a one-dimensional rod-shaped structure is formed.
After the hydrothermal reaction is finished, the product of the hydrothermal reaction is preferably subjected to post-treatment to obtain the nickel-manganese precursor.
In the present invention, the post-treatment preferably comprises cooling, filtration, washing and drying in this order.
The cooling rate is not particularly limited in the present invention, and the product of the hydrothermal reaction can be cooled to room temperature.
In the present invention, the filtration is preferably centrifugal filtration; the rotation speed of the centrifugal filtration is preferably 6000-8000 rpm, more preferably 6500-7500 rpm; the time for centrifugation is preferably 5-8 min, and more preferably 6-7 min. In the present invention, a solid product is obtained by filtering the product of the hydrothermal reaction.
In the present invention, the washing detergent is preferably distilled water; the number of washing is preferably 2 to 4. In the present invention, the washing may remove impurities such as nitrate ions.
The washing method is not particularly limited, and a washing method conventional in the art can be adopted. In the embodiment of the invention, the washing mode is preferably centrifugal washing by using distilled water, and particularly preferably a 50mL centrifuge tube is used, the consumption of distilled water is 25-35mL independently for each time, the centrifugation time is 5-7 minutes independently for each time, and the rotation speed of each centrifugation is 6500-7500 rpm independently.
The drying mode is not particularly limited, and the product with constant weight can be obtained. In the embodiment of the present invention, the drying is preferably air-blast drying; the drying temperature is preferably 70-100 ℃, and more preferably 80-90 ℃; the drying time is preferably 10-15 hours, and more preferably 12-13 hours.
After the nickel-manganese precursor is obtained, the nickel-manganese precursor is mixed with lithium carbonate and then calcined to obtain the lithium nickel manganese oxide cathode material. In the invention, the nickel-manganese precursor is mixed with lithium carbonate to obtain a uniform mixture (as shown in figure 1), and then the uniform mixture is calcined to generate a lithiation reaction to generate rod-shaped nickel lithium manganate (as shown in figure 1) assembled by nano particles.
In the present invention, the molar ratio of lithium atoms in the lithium carbonate to nickel nitrate and manganese nitrate is preferably 1.03 to 1.06:0.5:1.5, and more preferably 1.04 to 1.05:0.5: 1.5.
In the present invention, the lithium carbonate is preferably powdery lithium carbonate. In the present invention, the particle size of the lithium carbonate is not particularly limited, and commercially available lithium carbonate powder may be used.
In the present invention, the mixing is preferably a grinding mixing; the time for grinding and mixing is preferably 15-30 min, and more preferably 20-25 min. In the present invention, the grinding and mixing can ensure that the lithium carbonate powder is uniformly dispersed in the nickel-manganese precursor.
In the present invention, the calcination preferably includes a first calcination and a second calcination; the temperature of the first calcination is preferably 300-400 ℃, and more preferably 330-360 ℃; the first calcination time is preferably 2-3 h, and more preferably 2.3-2.7 h; the second calcining temperature is preferably 800-850 ℃, and more preferably 820-830 ℃; the second calcination time is preferably 6-8 h, and more preferably 6.5-7.5 h.
In the present invention, a stable matrix structure can be obtained by the first calcination at a lower temperature while effectively controlling Mn3+The content of the lead-free tin oxide can improve the conductivity of the electrode material and avoid structural collapse caused by the ginger-Taylor effect; after the temperature is raised to the second calcination temperature, a lithiation reaction occurs, carbon dioxide gas is released (as shown in a gray shading part on the left side in fig. 1), and impurities are decomposed at the same time, so that a stable and pure lithium nickel manganese oxide positive electrode material is obtained, wherein the obtained lithium nickel manganese oxide positive electrode material is a micron rod with a hierarchical structure, namely a micron rod assembled by nano particles (as shown in a structure in fig. 1).
In the invention, the heating rate of the temperature required by the temperature rise to the first calcination and the temperature required by the temperature rise to the second calcination is preferably 100-150 ℃/h, and more preferably 120-130 ℃/h.
The rod-shaped lithium nickel manganese oxide cathode material provided by the invention is mixed with carbon black to form a lithium ion battery cathode, so that the diffusion distance of lithium ions can be effectively shortened, and a stable structure is kept (as shown in a gray shading part on the right side in fig. 1).
The lithium nickel manganese oxide positive electrode material and the preparation method thereof provided by the present invention are described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 26.7mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 minutes; after the dropwise addition is finished, continuously stirring for 30min to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this embodiment is characterized by using low-power and high-power scanning electron microscopes, as shown in fig. 2, fig. 2a is a low-power SEM image, and fig. 2b is a high-power SEM image, and it can be seen from fig. 2 that the nickel-manganese precursor obtained in this embodiment is a one-dimensional micron rod with uniform size and smooth surface, the average length of the micron rod is 10 μm, and the average diameter is 800 nm.
The nickel-manganese precursor obtained in step (3) of this example is characterized by using a transmission electron microscope, and the obtained TEM image is shown in fig. 3, and it can be seen from fig. 3 that the nickel-manganese precursor has a uniform rod-like structure, which is consistent with the SEM image of fig. 2.
The shape of the lithium nickel manganese oxide positive electrode material obtained in this example is characterized by using a scanning electron microscope, and the result is shown in fig. 4, and it can be known from fig. 4 that the obtained lithium nickel manganese oxide positive electrode material still has a one-dimensional rod-like structure, the average length is 8 μm, and the average diameter is 2 μm. FIG. 4a is a low-power scanning electron microscope image, FIG. 4b is a high-power scanning electron microscope image, and it can be seen from FIG. 4b that the lithium nickel manganese oxide cathode material with a rod-like structure is composed of particles with an average diameter of 200nm and has a micron-nanometer assembled hierarchical structure.
The lithium nickel manganese oxide cathode material obtained in this example was characterized by using a transmission electron microscope, and the result is shown in fig. 5. From fig. 5 it can be clearly seen that the rod-like structures are assembled from nanoparticles, in accordance with the structure shown in fig. 4 b; in addition, it can be seen from fig. 5 that there are voids in the nanorods, indicating that the nanorods have a porous structure.
The lithium nickel manganese oxide obtained in the example was subjected to an X-ray diffraction test, and the result is shown in FIG. 6, wherein the characteristic peak of the obtained XRD pattern is identical to that of standard PDF card No.80-2162 (lithium nickel manganese oxide LiNi)0.5Mn1.5O4The standard card) completely corresponds to the standard card, and no impurity peak appears, which indicates that the lithium nickel manganese oxide obtained in the embodiment is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in this example was subjected to infrared and raman spectroscopy, and the results are shown in fig. 7 and 8. The characteristic peaks in FIGS. 7 and 8 illustrate that the product contains a certain amount of Mn3+Meanwhile, the Fd3m phase is also explained to be the main phase of the lithium nickel manganese oxide cathode material. The infrared spectrum of FIG. 7 was at 472,497,559,588 and 623cm-1Characteristic peaks appearing therein, Raman spectrum of FIG. 8398, 493 and 632cm-1The characteristic peaks appeared at (A) point to the Fd3m phase of the product and are in the Raman spectrum 588-623cm-1Region not appearing to point to P43The 32-phase peak separation result further confirms LiNi0.5Mn1.5O4The major phase in (1) is Fd3m phase.
And (3) electrochemical performance testing: preparing the lithium nickel manganese oxide positive electrode material obtained in the embodiment, conductive carbon black and a binder (PVDF) into uniform positive electrode slurry according to the mass ratio of 7:2:1, coating the uniform positive electrode slurry on an aluminum foil, and drying and tabletting to obtain a circular electrode plate with the load of 2-3 mg/cm2(ii) a Cutting the aluminum foil coated with the positive electrode slurry into a wafer serving as a positive electrode; the anode is sequentially connected with a diaphragm, a metallic lithium cathode and an electrolyte (namely 1 mol/LLIPF)6The solvent of the solution is formed by mixing Ethylene Carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1: 1) to form a lithium ion battery, and the electrochemical performance of the lithium ion battery is tested.
FIG. 9 is a cyclic voltammetry curve of a lithium ion battery at a sweep rate of 0.1mV/s over a range of 3.3V to 5.0V, with the redox peaks corresponding to the voltage plateaus in the charge-discharge curves of FIG. 11. Two sets of redox peaks were observed in total, with a sub-peak around 4.7V corresponding to Ni2+/Ni3+And Ni3+/Ni4+Two stages of redox reactions; the weak peak around 4.0V corresponds to Mn3+/Mn4+The small graph in FIG. 9 is a partial enlarged view of the process, and a slight fluctuation of the graph can be seen, indicating a small amount of Mn3+Is present. In the three-cycle process, the CV curve only shows slight change, the main oxidation-reduction peaks can be observed, and the graph lines almost follow the same trace, which indicates that the micron-nanometer assembly structure has better stability in the cycle process.
Fig. 10 is an ac impedance spectrum of the lithium ion battery, which is measured in a frequency range of 10mHz to 100kHz at room temperature, and it can be seen from the graph that the resistance of the lithium ion battery slightly increases after 5 cycles, and thereafter, the resistance of the battery is basically maintained with the increase of the number of cycles, which illustrates that the lithium nickel manganese oxide positive electrode material provided by the present invention has excellent cycle stability.
Fig. 11 is a charge-discharge curve of the lithium ion battery, and it can be seen from the graph that the charge specific capacities at 0.1, 1, 2 and 5C rates are 181, 156, 145 and 138mAh/g, respectively, and the corresponding discharge specific capacities are 158, 150, 141 and 135mAh/g, respectively. The above data are obtained in the first charge-discharge cycle at different magnifications, and the actual specific capacity can be seen to be close to the theoretical specific capacity; and in the first discharge process of low multiplying power, the charge-discharge specific capacity of the material can even slightly exceed the theoretical value, although in the second charge-discharge cycle process, the discharge specific capacity rapidly falls below the theoretical value, and the result still can show that the material has better specific capacity.
FIG. 12 is a graph of discharge rate performance of a lithium ion battery, showing that the lithium ion battery can provide reversible specific capacities of 144, 140, 131, 125, 118, and 112mAh/g when cycled for 5 times at 1, 2, 5, 15, and 20C rates in sequence; when the current is recovered to 1C multiplying power, the specific capacity can be basically recovered to 143mAh/g, which is close to the initial value, and the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent multiplying power performance.
Fig. 13 is a test chart of the cycle stability of the lithium ion battery, and it can be known from the test chart that after the lithium ion battery is cycled 200 times at a rate of 1C, the discharge specific capacity is stabilized at 142mAh/g, and the coulombic efficiency reaches 99.16%, which illustrates that the cycle stability of the lithium ion battery prepared by using the cathode material obtained in this embodiment is excellent.
Example 2
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 20mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 30min to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example was characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 11 μm and the average diameter is 900 nm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that shown in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 9 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 2.4 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 240 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in the example is subjected to an X-ray diffraction test, and the result is similar to that of FIG. 6, which shows that the lithium nickel manganese oxide obtained in the example is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 140, 139, 125, 123, 111 and 105mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, when the current is recovered to the multiplying power of 1C, the specific capacity can be basically recovered to 137mAh/g, which is close to the initial value, and the lithium ion battery prepared by the anode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 138mAh/g, and the coulombic efficiency reaches 98.78%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
Example 3
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 30mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 30min to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example was characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that shown in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 9 μm and the average diameter is 700 nm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 6 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 1.5 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 150 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in the example is subjected to an X-ray diffraction test, and the result is similar to that of FIG. 6, which shows that the lithium nickel manganese oxide obtained in the example is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 142, 138, 131, 125, 117 and 109mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, when the current is recovered to the multiplying power of 1C, the specific capacity can be basically recovered to 140mAh/g which is close to the initial value, and the lithium ion battery prepared by the anode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 138mAh/g, and the coulombic efficiency reaches 98.01%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
Example 4
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 26.7mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 8mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 30min to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example is characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that shown in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 12 μm and the average diameter is 1.5 μm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that shown in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 10 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 2.5 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 250 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in the example is subjected to an X-ray diffraction test, and the result is similar to that of FIG. 6, which shows that the lithium nickel manganese oxide obtained in the example is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 138, 131, 123, 116, 108 and 100mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, and when the current is recovered to the multiplying power of 1C, the initial value of 136mAh/g can be basically recovered by the specific capacity, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 135mAh/g, and the coulombic efficiency reaches 99.11%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
Example 5
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 26.7mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 1h to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example was characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 10.5 μm and the average diameter is 850 nm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 8.5 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 2.1 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 230 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in the example is subjected to an X-ray diffraction test, and the result is similar to that of FIG. 6, which shows that the lithium nickel manganese oxide obtained in the example is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 142, 139, 132, 126, 115 and 108mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, when the current is recovered to the multiplying power of 1C, the specific capacity can be basically recovered to 139mAh/g which is close to the initial value, and the lithium ion battery prepared by the anode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 138mAh/g, and the coulombic efficiency reaches 98.32%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
Example 6
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 26.7mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 2 hours to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example was characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 11 μm and the average diameter is 900 nm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 10 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 2.3 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 240 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in the example is subjected to an X-ray diffraction test, and the result is similar to that of FIG. 6, which shows that the lithium nickel manganese oxide obtained in the example is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 138, 132, 122, 121, 111 and 102mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, and when the current is recovered to the multiplying power of 1C, the initial value of 135mAh/g can be basically recovered by the specific capacity, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 134mAh/g, and the coulombic efficiency reaches 97.46%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
Example 7
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 26.7mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution；
(2) Under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 30min to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 24 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 350 ℃, performing first calcination for 2 hours, then heating to 800 ℃, and performing second calcination for 6 hours to obtain a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 350 ℃ and ramp up to 800 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example was characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that shown in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 10 μm and the average diameter is 800 nm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 8.5 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 2.1 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 210 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in this example was subjected to an X-ray diffraction test, and the results are similar to fig. 6, which shows that the lithium nickel manganese oxide obtained in this example is pure lithium nickel manganese oxideLithium LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 140, 138, 127, 122, 114 and 108mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, and when the current is recovered to the multiplying power of 1C, the initial value of 138mAh/g can be basically recovered by the specific capacity, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 136mAh/g, and the coulombic efficiency reaches 97.46%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
Example 8
(1) 2mmol of Ni (NO)3)2·6H2O、6mmol Mn(NO3)2·6H2Dissolving O and 26.7mmol of glycine in 50mL of deionized water to obtain a raw material mixed solution;
(2) under the stirring state, 10mL of sodium hydroxide solution with the concentration of 5mol/L is dripped into the raw material mixed solution, and the dripping time is 10 min; after the dropwise addition is finished, continuously stirring for 30min to obtain a suspension;
(3) transferring the suspension into a hydrothermal reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 160 ℃, and the time of the hydrothermal reaction is 20 hours; after the hydrothermal reaction is finished, cooling the reaction kettle to room temperature, and performing centrifugal separation to obtain a precipitate; washing the precipitate with distilled water for 3 times, and centrifugally washing with a 50mL centrifuge tube at a rotating speed of 7500rpm, wherein 25-35mL of water is used for washing each time; drying the washed precipitate at 80 ℃ for 12h to obtain a nickel-manganese precursor;
(4) uniformly mixing lithium carbonate and a nickel-manganese precursor by grinding, wherein the grinding time is 10-15 min, and the molar ratio of lithium to nickel to manganese in the lithium carbonate is 1.05:05: 1.5; placing the obtained mixture in a muffle furnace, heating to 300 ℃, performing first calcination for 2h, then heating to 850 ℃, performing second calcination for 6h, and obtaining a lithium nickel manganese oxide positive electrode material; the ramp rates for ramp up to 300 ℃ and ramp up to 850 ℃ are independently 150 ℃/h.
The surface morphology of the nickel-manganese precursor obtained in step (3) of this example was characterized by using low-power and high-power scanning electron microscopes, and the result is similar to that in fig. 2, where the average length of the nickel-manganese precursor obtained in this example is 11 μm and the average diameter is 950 nm.
The morphology of the lithium nickel manganese oxide positive electrode material obtained in the embodiment is characterized by using a scanning electron microscope, and the result is similar to that shown in fig. 4, the average length of the obtained lithium nickel manganese oxide positive electrode material is 11 μm, the average diameter of the obtained lithium nickel manganese oxide positive electrode material is 2.3 μm, and the lithium nickel manganese oxide positive electrode material with a rod-shaped structure is composed of particles with the average diameter of 250 nm.
The lithium nickel manganese oxide cathode material obtained in the embodiment is characterized by using a transmission electron microscope, and the result is similar to that in fig. 5, the rod-shaped structure is formed by assembling nanoparticles, and the micron rod has a porous structure.
The lithium nickel manganese oxide obtained in the example is subjected to an X-ray diffraction test, and the result is similar to that of FIG. 6, which shows that the lithium nickel manganese oxide obtained in the example is pure lithium nickel manganese oxide LiNi0.5Mn1.5O4。
The lithium nickel manganese oxide obtained in the example was subjected to infrared and raman spectroscopy, and the results were similar to those of fig. 7 and 8.
The lithium nickel manganese oxide cathode material obtained in the embodiment is assembled into a lithium ion battery according to the electrochemical performance test method described in the embodiment 1, and the electrochemical performance of the lithium nickel manganese oxide cathode material is tested, wherein the performances are similar to those of the embodiment 1. After 5 cycles of the obtained lithium ion battery, the resistance of the battery is basically unchanged, and the lithium ion battery has excellent cycling stability; the lithium ion battery can provide reversible specific capacity of 138, 136, 130, 123, 113 and 106mAh/g after 5 times of circulation under the multiplying power of 1, 2, 5, 15 and 20C in sequence, and when the current is recovered to the multiplying power of 1C, the initial value of 134mAh/g can be basically recovered by the specific capacity, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent multiplying power performance; after the lithium ion battery is cycled for 200 times under the multiplying power of 1C, the discharge specific capacity is stabilized at 132mAh/g, and the coulombic efficiency reaches 96.46%, which shows that the lithium ion battery prepared by the cathode material obtained in the embodiment has excellent cycling stability.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The lithium nickel manganese oxide positive electrode material is a micron rod assembled by lithium nickel manganese oxide nano particles, the average particle size of the lithium nickel manganese oxide nano particles is 150-250 nm, the average diameter of the micron rod is 1.5-2.5 microns, and the average length of the micron rod is 6-12 microns;
the preparation method of the lithium nickel manganese oxide positive electrode material comprises the following steps:
(1) dissolving nickel nitrate, manganese nitrate and glycine in water to obtain a raw material mixed solution;
(2) dropwise adding a strong base solution into the raw material mixed solution, and carrying out hydrothermal reaction to obtain a nickel-manganese precursor;
(3) and mixing the nickel-manganese precursor with lithium carbonate, and calcining to obtain the lithium nickel manganese oxide positive electrode material.
2. A preparation method of a lithium nickel manganese oxide positive electrode material comprises the following steps:
(1) dissolving nickel nitrate, manganese nitrate and glycine in water to obtain a raw material mixed solution;
(2) dropwise adding a strong base solution into the raw material mixed solution, and carrying out hydrothermal reaction to obtain a nickel-manganese precursor;
(3) and mixing the nickel-manganese precursor with lithium carbonate, and calcining to obtain the lithium nickel manganese oxide positive electrode material.
3. The preparation method according to claim 2, wherein the molar ratio of the nickel nitrate to the glycine is 1: 10-15.
4. The method of claim 2, wherein the strong alkaline solution is an aqueous solution of sodium hydroxide and/or potassium hydroxide.
5. The preparation method according to claim 4, wherein the concentration of the alkali in the strong alkali solution is 5-8 mol/L; the ratio of the amount of the nickel nitrate to the volume of the strong alkali solution is 1mmol: 3-5 mL.
6. The preparation method according to claim 2, wherein the temperature of the hydrothermal reaction is 120 to 160 ℃ and the time of the hydrothermal reaction is 20 to 26 hours.
7. The production method according to claim 2, characterized in that the calcination includes a first calcination and a second calcination; the temperature of the first calcination is 300-400 ℃, and the time of the first calcination is 2-3 h; the temperature of the second calcination is 800-850 ℃, and the time of the second calcination is 6-8 h.
8. The production method according to claim 7, wherein the temperature increase rate for increasing the temperature to the temperature required for the first calcination and the second calcination is independently 100 to 150 ℃/h.
9. The preparation method according to claim 2, wherein the molar ratio of lithium atoms in the lithium carbonate to the nickel nitrate and the manganese nitrate is 1.03-1.06: 0.5: 1.5.
10. The production method according to claim 2 or 9, wherein the mixing in the step (3) is a milling mixing.
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| CN104409717A (en) * | 2014-11-06 | 2015-03-11 | 奇瑞汽车股份有限公司 | Nano rod-shaped nickel-lithium manganate cathode material and preparation method thereof |
| CN104966830A (en) * | 2015-05-25 | 2015-10-07 | 哈尔滨工业大学 | Preparation method and application of rod-shaped lithium nickel manganese oxide material |
| CN106505186A (en) * | 2016-11-28 | 2017-03-15 | 湖南大学 | A kind of lithium iron phosphate positive material of in-stiu coating graphene film and preparation method thereof |
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