CN111924810B - Iron-cobalt bimetallic selenide nano material, preparation method thereof and lithium ion battery - Google Patents
Iron-cobalt bimetallic selenide nano material, preparation method thereof and lithium ion battery Download PDFInfo
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Abstract
The invention provides an iron-cobalt bimetallic selenide nano material, a preparation method thereof and a lithium ion battery. The preparation method of the iron-cobalt bimetallic selenide nano material provided by the invention comprises the following steps: heating ferric acetylacetonate, cobalt acetylacetonate and dibenzyl diselenide in solvent to react and form Fe2CoSe4And (3) nano materials. The invention adopts specific ferric acetylacetonate, nickel acetylacetonate and dibenzyl diselenide as precursor source, and makes them produce reaction in solvent system, and can directly synthesize Fe by one-step process2CoSe4The nano material greatly simplifies the operation and can effectively improve Fe2CoSe4Crystallinity and purity of the nanomaterial. Fe prepared by the invention2CoSe4The nano material is used as a negative electrode material of the lithium ion battery, and can improve the lithium storage specific capacity, the rate capability and the cycle performance of the battery.
Description
Technical Field
The invention relates to the technical field of lithium ion battery materials, in particular to an iron-cobalt bimetallic selenide nano material, a preparation method thereof and a lithium ion battery.
Background
Rechargeable Lithium Ion Batteries (LIBs) have been occupying the consumer market for intelligent electronic devices since their commercialization by Sony corporation in 1990, and have even been successfully used in Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) in recent years. Generally, lithium ion batteries are made of a negative electrode material (e.g., graphite), a positive electrode material (e.g., LiCoO)2) An electrolyte and a separator. The commercial lithium ion battery completes charging and discharging according to a rocking chair type mechanism, and electrons can form continuous current through an external circuit to supply electric equipment by virtue of lithium ions which continuously migrate in the battery. It is obvious that the electrochemical performance of a lithium ion battery strongly depends on the lithium storage capacity of the negative electrode material.
Due to the lower theoretical capacity, commercial graphite (372mAh/g) negative electrodes have failed to meet the demand for further development of lithium ion batteries. In order to increase the energy/power density of lithium ion batteries, the development of new anode materials having excellent kinetics and lithium storage properties is imminent. In general, three reaction mechanisms of intercalation, transformation and alloying exist in the negative electrode material of the lithium ion battery. Specifically, the negative electrode material belonging to the intercalation mechanism often has an obvious charge/discharge platform and a lower theoretical capacity, such as graphene, titanium oxide and other materials. The negative electrode material belonging to the conversion mechanism has a high theoretical capacity due to the occurrence of a multiple electron reaction during the cycle, and is, for example, a metal chalcogenide, a metal oxide, or the like. The theoretical capacity of the materials of the alloy system is generally higher, but the reaction process is often accompanied by phenomena such as severe volume collapse of electrode materials, for example, materials such as red phosphorus, tin, silicon, antimony and the like. Based on the large background and the unique electrochemical reaction characteristics, the transition metal selenide compound with higher theoretical capacity and the composite material thereof become the lithium ion battery cathode material with increased application potential. Therefore, the preparation of transition metal selenides is of great significance.
However, for the preparation of transition metal selenides, the ternary double transition metal selenides are difficult to synthesize pure phases in laboratory preparation, and because the formation enthalpy of the binary transition metal selenides is far negative to that of the ternary double transition metal selenides, the binary transition metal selenides are easier to synthesize compared with the ternary double transition metal selenides, so that in the preparation of the ternary double transition metals, mixed phases of a plurality of binary selenides are often obtained. Moreover, the preparation methods disclosed in the current research are also more complex multi-step reaction methods, for example, for iron-nickel selenide, a bimetallic intermediate is obtained by calcination or water/solvothermal method, and then a target product is obtained by selenization, so that the process is complex, and the purity and crystallinity of the obtained product are poor.
Disclosure of Invention
In view of the above, the present invention provides a fe-co bimetallic selenide nano material, a preparation method thereof and a lithium ion battery. The preparation method provided by the invention can improve the crystallinity and purity of the product, greatly simplifies the preparation process, and can realize one-step synthesis of Fe2CoSe4A pure phase nanomaterial. Fe prepared by the invention2CoSe4The nano material is used as a negative electrode material of the lithium ion battery, and can improve the lithium storage specific capacity, the rate capability and the cycle performance of the battery.
The invention provides a preparation method of an iron-cobalt bimetallic selenide nano material, which comprises the following steps:
heating ferric acetylacetonate, cobalt acetylacetonate and dibenzyl diselenide in solvent to react and form Fe2CoSe4And (3) nano materials.
Preferably, the solvent is oleylamine.
Preferably, the temperature of the heating reaction is 270-290 ℃.
Preferably, the heating rate of the heating reaction is 1-10 ℃/min.
Preferably, the heat preservation time in the heating reaction is 20-60 min.
Preferably, the reaction is carried out in an inert atmosphere;
the reaction is carried out under stirring conditions; the stirring speed is 150-550 rpm.
Preferably, the molar ratio of the ferric acetylacetonate to the nickel acetylacetonate to the dibenzyl diselenide is 0.1: 0.05: 0.1;
the dosage ratio of the nickel acetylacetonate to the solvent is (0.05-0.1) mmol to (5-10) mL.
Preferably, preheating is carried out before the reaction;
the preheating temperature is 120-150 ℃, and the time is more than 5 min.
The invention also provides the iron-nickel bimetallic selenide Fe prepared by the preparation method in the technical scheme2CoSe4And (3) nano materials.
The invention also provides a lithium ion battery, and the negative electrode material in the lithium ion battery is the iron-nickel bimetallic selenide Fe in the technical scheme2CoSe4And (3) nano materials.
The invention provides Fe-Co bimetallic selenide Fe2CoSe4A method for preparing a nano-material, which comprises the following steps,the method comprises the following steps: heating ferric acetylacetonate, cobalt acetylacetonate and dibenzyl diselenide in solvent to react and form Fe2CoSe4And (3) nano materials. The invention adopts a specific precursor source-ferric acetylacetonate [ Fe (acac)3]Cobalt acetylacetonate [ Co (acac)2]And dibenzyl diselenide [ (PhCH)2)2Se2]The reaction is carried out in a solvent system, and Fe can be directly synthesized in one step2CoSe4The nano material greatly simplifies the operation and can effectively improve Fe2CoSe4Crystallinity and purity of the nanomaterial.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a Transmission Electron Microscope (TEM) test chart of the product obtained in example 1;
FIG. 2 is a High Resolution Transmission Electron Microscopy (HRTEM) test chart of the product obtained in example 1; wherein, fig. 2a is a high-resolution transmission electron microscope image of the material in different areas under different magnifications, fig. 2b is a fast fourier transform test image of a selected area in the high-resolution image, and fig. 2c is a Mapping distribution diagram of sample constituent elements;
FIG. 3 is an X-ray diffraction pattern (XRD) of the product obtained in example 1;
FIG. 4 is a diagram of Ultraviolet Photoelectron Spectroscopy (UPS) of the product obtained in example 1; wherein FIG. 4a shows the near Fermi level (E) obtained from a sample through UPSF) And the top of the price belt (E)v) FIG. 4b shows the secondary electron cut-off (E) obtained by UPS of the sampleonset) A spectrogram;
FIG. 5 is an X-ray photoelectron spectroscopy XPS chart of the product obtained in example 1; wherein, FIGS. 5a, 5b, and 5c are XPS fine spectra of Fe2p, Co 2p, and Se3d, respectively;
FIG. 6 shows Fe obtained in example 12CoSe4A multiplying power performance test chart of the lithium ion battery assembled by the material;
FIG. 7 shows Fe obtained in example 12CoSe4A cycle stability test chart of the lithium ion battery assembled by the material under the current density of 200 mA/g;
FIG. 8 shows Fe obtained in example 12CoSe4And (3) a cycle stability test chart of the lithium ion battery assembled by the material under the current density of 4A/g.
Detailed Description
The invention provides Fe-Co bimetallic selenide Fe2CoSe4A method of preparing a nanomaterial comprising:
heating ferric acetylacetonate, cobalt acetylacetonate and dibenzyl diselenide in solvent to react and form Fe2CoSe4And (3) nano materials.
The invention adopts a specific precursor source-ferric acetylacetonate [ Fe (acac)3]Cobalt acetylacetonate [ Co (acac)2]And dibenzyl diselenide [ (PhCH)2)2Se2]The reaction is carried out in a solvent system, and Fe can be directly synthesized in one step2CoSe4Nano material, and Fe capable of being effectively improved2CoSe4The crystallinity and purity of the nano material. Through the research of the applicant, when other conventional iron sources, cobalt sources or selenium sources are adopted, Fe can not be synthesized through the one-step reaction method of the application2CoSe4And (3) nano materials. The sources of the iron acetylacetonate, the cobalt acetylacetonate and the dibenzyl diselenide are not particularly limited, and the iron acetylacetonate, the cobalt acetylacetonate and the dibenzyl diselenide are commercially available products.
In the invention, the dosage ratio of the ferric acetylacetonate, the cobalt acetylacetonate and the dibenzyl diselenide is carried out according to a stoichiometric ratio, and specifically the molar ratio is 0.1: 0.05: 0.1.
In the invention, the solvent is oleylamine. The three precursor sources can be better combined in a specific oleylamine system to realize Fe2CoSe4And (4) synthesizing the nano material. In the invention, the dosage ratio of the cobalt acetylacetonate to the solvent is preferably (0.05-0.1) mmol to (5-10) mL.
In the invention, the reaction method is a hydrothermal reflux method, and the adopted reaction device is not particularly limited and only needs to be a reaction device used in the conventional heating reflux method in the field; specifically, the reaction apparatus may be constructed by a three-necked flask and a reflux apparatus.
In the present invention, it is preferable to preheat the reaction mixture before the heating reaction. The preheating temperature is preferably 120-150 ℃; in some embodiments of the invention, the temperature of the preheating is 120 ℃, 135 ℃ or 150 ℃. The preheating time is preferably more than 5min, and more preferably 20-30 min. The heating rate of the preheating is preferably 1-10 ℃/min. The low boiling point impurities such as water, dissolved oxygen and the like in the system are removed by preheating.
After preheating, the invention carries out heating reaction. The heating rate of the heating reaction is preferably 1-10 ℃/min; in some embodiments of the invention, the ramp rate is 1 deg.C/min, 5 deg.C/min, or 10 deg.C/min. The target temperature of the heating reaction is preferably 270-290 ℃; in some embodiments of the invention, the target temperature is 270 ℃, 280 ℃, or 290 ℃. After the temperature is raised to the target temperature, the heat preservation time is preferably 20-60 min; in some embodiments of the invention, the incubation is for 20min, 40min, or 60 min. Through the reaction process, the precursor completes the reaction to generate Fe2CoSe4The nano material exists in the form of precipitate in the reaction system.
In the present invention, the heating reaction is preferably carried out under an inert atmosphere. The inert gas for providing the inert atmosphere in the present invention is not particularly limited in kind, and may be any conventional inert gas known to those skilled in the art, such as nitrogen or argon. The pressure of the inert gas in the reaction system is not particularly limited, and may be normal pressure. In the present invention, the heating reaction is preferably carried out under stirring. The stirring speed is preferably 150-550 rpm.
In the present invention, the above-mentioned preheating process is preferably also carried out under an inert atmosphere and under stirring conditions. The inert atmosphere and the stirring conditions are the same as those described above and will not be described herein.
In the present invention, after the reaction is completed, it is preferable to further perform a post-treatment. What is needed isThe post-treatment comprises the following steps: for Fe obtained by reaction2CoSe4Washing the nanometer material precipitate, solid-liquid separating and drying. The washing liquid used for the washing is preferably an organic solvent. The invention has no special limitation on the type of the organic solvent, and can wash out the residual solvent in the reaction system. The solid-liquid separation is preferably centrifugal separation. The drying is preferably vacuum drying; the drying temperature is preferably 40-70 ℃. After the post-treatment, Fe is obtained2CoSe4And (3) nano materials.
In the invention, the obtained Fe2CoSe4 nano material is a nano sheet material, and the size of the nano sheet is 25-35 nm.
The preparation method provided by the invention has the following beneficial effects:
1. can obtain Fe2CoSe4Pure phase ternary material and improves the crystallinity of the material.
2. The preparation method is a one-step synthesis method, is simple to operate, has mild conditions, and is convenient for large-scale production and application.
The invention also provides the iron-cobalt bimetallic selenide Fe prepared by the preparation method in the technical scheme2CoSe4And (3) nano materials. Fe prepared by the invention2CoSe4The ternary material has high crystallinity and high purity, and can improve the lithium storage specific capacity, the rate capability and the cycle performance of the lithium ion battery.
The invention also provides a lithium ion battery, wherein the cathode material is the Fe-Co bimetallic selenide Fe in the technical scheme2CoSe4And (3) nano materials.
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
Example 1
1.1 preparation
0.1mmol (35.3mg) of iron acetylacetonate, 0.05mmol (12.8mg) of cobalt acetylacetonate, 0.1mmol (34.0mg) of dibenzyldiselenide and 5.0mL of oleylamine were takenPutting the solvent into a 100mL three-neck flask, and setting up a reflux device. Under the conditions of argon atmosphere (the air pressure in the flask is normal pressure) and magnetic stirring (the speed is 350rpm), the device is heated to 135 ℃ at a constant speed (the speed is 10 ℃/min) and is kept for 20 min. Then continuously heating to 280 ℃ at the speed of 10 ℃/min, and preserving heat for 40 min. Then naturally cooling to room temperature, washing the precipitate in the three-mouth bottle for a plurality of times by using normal hexane and ethanol solution, and then centrifugally separating and vacuum drying to obtain Fe2CoSe4And (3) nano materials.
1.2 characterization and testing
(1) The transmission electron microscope test of the obtained product is shown in figure 1, and figure 1 is a Transmission Electron Microscope (TEM) test chart of the product obtained in example 1. As can be seen, the obtained product is a nanosheet with uniform morphology and a size of about 30 nm.
(2) The obtained product is subjected to a High Resolution Transmission Electron Microscope (HRTEM) test, and a Fast Fourier Transform (FFT) is performed on a selected region in a high resolution image, and the result is shown in fig. 2, fig. 2 is a High Resolution Transmission Electron Microscope (HRTEM) test image of the product obtained in example 1, wherein fig. 2a is a high resolution transmission electron microscope image of the material in different regions under different magnifications, fig. 2b is a fast fourier transform test image of the selected region in the high resolution image, and fig. 2c is a Mapping distribution diagram of constituent elements of the sample.
In FIG. 2a, the lattice fringes at 0.542nm, 0.202nm, 0.269nm and 0.262nm correspond exactly to Fe2CoSe4The (002), (114), (-112) and (202) crystal planes of (A). A certain high-resolution fringe region is selected for fast Fourier transform, as shown in FIG. 2b, it can be seen that the obtained product conforms to pure phase Fe2CoSe4The monoclinic system of the ternary material. Fig. 2c is a distribution of three basic elements of Fe, Co and Se constituting the sample, showing that each element is uniformly distributed in the nanosheet.
(3)Fe2CoSe4The ternary material belongs to I2/m space group, and the obtained Fe2CoSe4The product was subjected to X-ray diffraction (XRD) measurement, and the result is shown in FIG. 3, and FIG. 3 is an X-ray diffraction pattern (XRD) pattern of the product obtained in example 1. It can be seen that at 16.293 °, 16.769 °, 26.458 °, 29.032 °, 33.234 °, 33.936 °, 3The 2 θ peaks at 5.350 °, 39.899 °, 44.005 °, 44.790 °, 50.343 °, 51.605 °, 59.471 ° and 63.322 ° correspond precisely to Fe2CoSe4(002), (101), (011), (200), (-112), (202), (013), (211), (-114), (-303), (020), (116), and (314) diffractive crystal planes (JCPDS 01-089-2CoSe4Is phase pure and has high crystallinity. In addition, the more strongly diffracting (002), (114), (-112) and (202) facets have also been captured by the high resolution plot shown in FIG. 2a, again demonstrating pure phase Fe2CoSe4Successful preparation of ternary materials.
Yield: according to the preparation conditions in 1.1, the actual yield of the objective product was 21mg and the theoretical yield was 24mg, and thus the yield of the objective product was 87.5%.
(4) The Ultraviolet Photoelectron Spectroscopy (UPS) of the product is shown in FIG. 4, and FIG. 4 is the Ultraviolet Photoelectron Spectroscopy (UPS) of the product obtained in example 1; wherein FIG. 4a shows the near Fermi level (E) obtained from a sample through UPSF) And the top of the price belt (E)v) FIG. 4b shows the secondary electron cut-off (E) obtained by UPS of the sampleonset) Spectra. By linear extrapolation of the curves of FIGS. 4a and 4b using Au as reference, Fe2CoSe4Has a valence band relative Fermi level of 0.677eV (FIG. 4a), and E thereofonsetThe value was 35.578eV (FIG. 4 b). The work function (phi) reflects the electron dynamics information of the sample surface, and Fe can be obtained according to the formula phi-hv-Eonset (the formula hv-40.0 eV is the photon energy)2CoSe4The work function of the material is 4.422eV, which shows that the material has better electron conductivity.
(5) The X-ray photoelectron spectroscopy (XPS) of the obtained product is shown in FIG. 5, and FIG. 5 is an X-ray photoelectron spectroscopy XPS of the product obtained in example 1; wherein, fig. 5a, 5b and 5c are XPS fine spectrograms of Fe2p, Co 2p and Se3d, respectively. X-ray photoelectron spectroscopy (XPS) reflects information such as the composition of elements in a material and the chemical state of each element. For Fe2CoSe4Ternary material, in the fine spectrum of Fe2p (FIG. 5a), consisting of Fe2p1/2And Fe2p3/2Respectively contains Fe2+Characteristic peaks of valence states (at the binding energies of 706.98eV and 719.92 eV) and from Fe3+Characteristic peaks of valence states (at the binding energies of 710.69eV and 724.16 eV). In the fine spectrum of Co 2p (FIG. 5b), Co 2p is present in addition to two satellite peaks that accompany it1/2And Co 2p3/2Can also be attributed to Co2+Characteristic peaks of valence states (at the binding energies of 778.39eV and 793.53 eV) and of valence states derived from Co3+Characteristic peaks of valence states (at the binding energies of 780.45eV and 796.22 eV). The Se3d XPS fine spectrogram (figure 5c) of the ternary material has a separable peak of Se3d3/2And Se3d5/2Two characteristic peaks, located at the binding energies of 55.23eV and 54.44eV, respectively.
(6) The obtained product was subjected to Inductively Coupled Plasma (ICP) test, and the results were the same as those obtained by X-ray diffraction energy Spectroscopy (EDX) and X-ray photoelectron Spectroscopy (XPS), i.e., the atomic number ratio of the basic elements in the prepared sample was close to 2: 1: 4 (Fe: Co: Se), which was consistent with the molar ratio of the reaction precursor raw materials, as shown in Table 1.
Table 1 elemental testing of the product obtained in example 1
According to the characterization test results, the Fe-Co bimetallic selenide Fe can be successfully prepared by the one-step hydrothermal solution reflux method2CoSe4The nano-sheet material has short reaction time and high efficiency; and the synthesized Fe2CoSe4The product has high crystallinity and high purity.
1.3 electrochemical Performance testing
Mixing Fe2CoSe4The materials, the acetylene black and the PVDF are uniformly mixed according to the mass ratio of 80: 10 to form the cathode slurry. Coating the obtained negative electrode slurry on a copper foil at 80 DEG CAnd drying to obtain the negative pole piece. After that, the cell was transferred to an argon glove box for cell assembly. In the assembly, lithium foil was used as a counter electrode, Celgard2400 was used as a separator, and LiPF was used6The solution was an electrolyte (concentration 1.0M; solvent was a mixture of dimethyl carbonate and ethylene carbonate in a volume ratio of 1: 1; and the entire electrolyte also contained 5 wt% fluoroethylene carbonate). And assembling to obtain the button type half cell. And on a blue test system, respectively completing charge-discharge circulation of the battery under a constant current and rate performance test under a series of currents, wherein the charge-discharge voltage range is 0.01-3V.
(1)Fe2CoSe4The rate capability of the ternary material is shown in FIG. 6, and FIG. 6 shows Fe obtained in example 12CoSe4And (3) a rate performance test chart of the lithium ion battery assembled by the material. It can be seen that the specific capacity of the material is up to 1000mAh/g under the condition that the current density is 0.1A/g; when the current density is gradually increased to the maximum value of 10A/g, the discharge specific capacity still reaches 390mAh/g and is kept stable; when the current density returns to the original 0.1A/g, the specific capacity can be basically recovered. Fe at a current density of 200mAh/g2CoSe4After the lithium ion battery assembled by the material is subjected to an irreversible electrochemical process initiated by SEI, structural rearrangement and the like, the discharge specific capacity of the lithium ion battery is maintained to be about 950mAh/g, and the coulombic efficiency is close to 100% all the time. In the next 100-circle stability test, the specific capacity of the electrode is hardly changed, the capacity can be kept at about 1000mAh/g after the circulation is finished, and the coulombic efficiency is close to 100%. Even if the material is cycled for a long time of 500 circles, the specific discharge capacity of the material is still as high as 900mAh/g, and the capacity retention rate is about 90 percent. Evidence of Fe2CoSe4Excellent stability.
(2) Stability tests were performed on the assembled half-cells at low current density and high current density, respectively, with the results shown in fig. 7 and 8, respectively; wherein, FIG. 7 shows Fe obtained in example 12CoSe4The lithium ion battery assembled by the material has a cycle stability test chart under the current density of 200mA/g, and FIG. 8 shows Fe obtained in example 12CoSe4The lithium ion battery assembled by the material is at the current density of 4A/gThe cycle stability test chart of (1).
As can be seen from FIG. 7, when the current density is 200mA/g, Fe after undergoing irreversible electrochemical processes initiated initially by SEI, structural rearrangement, etc2CoSe4The specific discharge capacity of the electrode is maintained to be about 950mAh/g, and the coulombic efficiency is close to 100 percent all the time. Even after long-time circulation of 500 circles, the discharge specific capacity of the ternary material is still as high as about 900mAh/g, and the capacity retention rate is about 90%. Because of the higher polarizability of sulfur and selenium materials, the invention also tests Fe under higher current density2CoSe4The cycle stability of (2) as shown in FIG. 8, it can be seen that at a current density of 4A/g, Fe2CoSe4The first circle has a discharge specific capacity up to 770mAh/g, a charge specific capacity of 590mAh/g and a coulombic efficiency of about 77%. In a reversible cycle followed by approximately 2240 cycles, Fe2CoSe4The specific discharge capacity can be maintained at about 600mAh/g, and the fluctuation range is not large, which shows that the material has excellent lithium storage stability in a wide condition.
The above test results demonstrate that the Fe-Co bimetallic selenide Fe synthesized by the invention2CoSe4The nano sheet material has higher specific capacity, excellent rate capability and good cycling stability, and is a lithium ion battery cathode material with great potential.
Example 2
1.1 preparation
A100 mL three-necked flask was charged with 0.1mmol (35.3mg) of iron acetylacetonate, 0.05mmol (12.8mg) of cobalt acetylacetonate, 0.1mmol (34.0mg) of dibenzyldiselenide and 10.0mL of oleylamine solvent, and a reflux apparatus was set up. Under the conditions of argon atmosphere (the air pressure in the flask is normal pressure) and magnetic stirring (the speed is 450rpm), the device is heated to 120 ℃ at a constant speed (the speed is 5 ℃/min) and is kept for 25 min. Then the temperature is continuously increased to 270 ℃ at the speed of 5 ℃/min, and the temperature is kept for 60 min. Then naturally cooling to room temperature, washing the precipitate in the three-mouth bottle for a plurality of times by using normal hexane and ethanol solution, and then centrifugally separating and vacuum drying to obtain Fe2CoSe4And (3) nano materials.
1.2 characterization and testing
According to the examples1, the results show that the obtained product is a nano flaky material, the shape is uniform, and the size is about 30 nm. The obtained product is in accordance with pure phase Fe2CoSe4The monoclinic system of the nano material; all elements are uniformly distributed in the nano-sheets. No miscellaneous peak which does not belong to a target product is observed in an XRD spectrogram, which indicates that the prepared Fe2CoSe4Is a pure phase and has a high degree of crystallinity. The yield thereof was found to be 85%. The Inductively Coupled Plasma (ICP) test results were the same as those obtained by X-ray diffraction energy spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), and the atomic number ratio of the basic elements in the prepared sample was close to 2: 1: 4 (Fe: Co: Se), consistent with the molar ratio of the reactive precursor raw materials.
1.3 electrochemical Performance testing
The electrochemical performance test was carried out according to the performance test method in example 1, and the results showed that, similarly to the electrochemical analysis results in example 1, Fe, which is the target product2CoSe4The lithium ion battery cathode material also has higher specific capacity, excellent rate capability and good cycling stability.
Example 3
1.1 preparation
A100 mL three-necked flask was charged with 0.1mmol (35.3mg) of iron acetylacetonate, 0.05mmol (12.8mg) of cobalt acetylacetonate, 0.1mmol (34.0mg) of dibenzyldiselenide and 5.0mL of oleylamine solvent, and a reflux apparatus was set up. Under the conditions of argon atmosphere (the air pressure in the flask is normal pressure) and magnetic stirring (the speed is 150rpm), the device is heated to 150 ℃ at a constant speed (the speed is 1 ℃/min) and is kept for 30 min. Then the temperature is continuously increased to 290 ℃ at the speed of 1 ℃/min, and the temperature is kept for 20 min. Then naturally cooling to room temperature, washing the precipitate in the three-mouth bottle for a plurality of times by using normal hexane and ethanol solution, and then centrifugally separating and vacuum drying to obtain Fe2CoSe4And (3) nano materials.
1.2 characterization and testing
The characterization test methods of example 1 were followed, and the results showed that the obtained product was a nano-sheet material with a uniform shape and a size of about 30 nm. The obtained product is in accordance with pure phase Fe2CoSe4The monoclinic system of the nano material; all elements are uniformly distributed in the nano-sheets. No miscellaneous peak which does not belong to a target product is observed in an XRD spectrogram, which indicates that the prepared Fe2CoSe4Is a pure phase and has a high degree of crystallinity. The yield thereof was found to be 86%. The Inductively Coupled Plasma (ICP) test results were the same as those obtained by X-ray diffraction energy spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), and the atomic number ratio of the basic elements in the prepared sample was close to 2: 1: 4 (Fe: Co: Se), consistent with the molar ratio of the reactive precursor raw materials.
1.3 electrochemical Performance testing
The electrochemical performance test was carried out according to the performance test method in example 1, and the results showed that, similarly to the electrochemical analysis results in example 1, Fe, which is the target product2CoSe4The lithium ion battery cathode material also has higher specific capacity, excellent rate capability and good cycling stability.
Comparative example 1
The procedure of example 1 was followed except that the iron source was replaced with ferric nitrate [ Fe (NO)3)3]The cobalt source is replaced by cobalt nitrate [ Co (NO)3)2]The materials are also fed according to the stoichiometric ratio.
The product obtained was characterized according to the characterization test method in example 1, and the results show that the characterization data of the product in comparative example 1 is related to Fe2CoSe4The standard data of (A) are inconsistent, indicating that the resulting product is not phase pure Fe2CoSe4A material. It was demonstrated that pure phase Fe could not be synthesized by the one-step method of the present invention using other conventional iron and cobalt sources2CoSe4A material.
Comparative example 2
The procedure is as in example 1 except that the selenium source is replaced by selenium powder and the oleylamine solvent is replaced by octadecene solvent, again dosed stoichiometrically.
The product obtained was characterized according to the characterization test method in example 1, and the results show that the characterization data of the product in comparative example 2 is related to Fe2CoSe4The standard data of (A) are inconsistent, indicating that the resulting product is not phase pure Fe2CoSe4A material. It was demonstrated that pure phase Fe could not be synthesized by the one-step method of the present invention using other conventional selenium sources and solvents2CoSe4A material.
Comparative example 3
The procedure of example 1 was followed except that the reaction temperature was adjusted to 240 ℃.
The product obtained was characterized according to the characterization test method in example 1, and the results show that the characterization data of the product in comparative example 3 is comparable to Fe2CoSe4The standard data of (A) are inconsistent, indicating that the resulting product is not phase pure Fe2CoSe4Material with binary selenide. Proves that if the reaction temperature is too low, pure-phase Fe can not be synthesized2CoSe4A material.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A preparation method of an iron-cobalt bimetallic selenide nano material is characterized by comprising the following steps:
mixing and preheating iron acetylacetonate, cobalt acetylacetonate, dibenzyl diselenide and solvent, heating and reacting to form Fe2CoSe4A nanomaterial;
the heating reaction is a one-step reaction, and the temperature of the heating reaction is 270-290 ℃;
the solvent is oleylamine;
the reaction is carried out in an inert atmosphere;
the reaction is carried out under stirring conditions; the stirring speed is 150-550 rpm.
2. The method according to claim 1, wherein the heating rate of the heating reaction is 1 to 10 ℃/min.
3. The method according to claim 1, wherein the heat-retaining time in the heating reaction is 20 to 60 min.
4. The method of claim 1, wherein the molar ratio of iron acetylacetonate, cobalt acetylacetonate, and dibenzyldiselenide is 0.1: 0.05: 0.1;
the dosage ratio of the cobalt acetylacetonate to the solvent is (0.05-0.1) mmol to (5-10) mL.
5. The preparation method according to claim 1, wherein the preheating temperature is 120-150 ℃ and the preheating time is more than 5 min.
6. Fe-Co bimetallic selenide Fe prepared by the preparation method of any one of claims 1 to 52CoSe4And (3) nano materials.
7. A lithium ion battery, characterized in that the negative electrode material in the lithium ion battery is the Fe-Co bimetallic selenide Fe of claim 62CoSe4And (3) nano materials.
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