CN109065876B - Copper sulfide/nitrogen-doped graphite nanocomposite material and preparation method and application thereof - Google Patents
Copper sulfide/nitrogen-doped graphite nanocomposite material and preparation method and application thereof Download PDFInfo
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Abstract
The application discloses a copper sulfide/nitrogen-doped graphite nano composite material, wherein copper sulfide with the average particle size of 10-20nm grows on the surface of nitrogen-doped graphite. The material is used as a lithium ion negative electrode material to assemble a battery, and the reversible charge-discharge capacity can reach 600mAh/g after 300 charge-discharge cycles under the current density of 200 mA/g; at a high current density of 2000mA/g, the capacity could still be maintained at 530mAh/g over 1000 cycles, which is much higher than many of the previously reported capacity of CuS based materials. The composite material prepared by the method is expected to be applied to the next generation of lithium ion battery cathode materials.
Description
Technical Field
The application relates to a copper sulfide/nitrogen-doped graphite nanocomposite material and a preparation method and application thereof, belonging to the field of materials.
Background
CuS is a natural mineral with abundant reserves, and has the characteristics of low price and low toxicity. In recent years, with the intensive research on electrode materials for lithium ion batteries, the capacity of a cathode material, CuS, which is a typical conversion reaction characteristic, is much higher than that of a conventional intercalation-type reaction electrode material, such as LiCoO2,LiFePO4And received wide attention from researchers. Unfortunately, the CuS has poor cycle stability due to the defects of large volume change, polysulfide dissolution and the like in the charge and discharge reaction processes, and the application of the material is seriously hindered. In order to solve the problem, researchers design and synthesize some CuS nanostructures (J.Power Sources,2016,306, 408-. The main reason for this phenomenon is that the fast nucleation and growth kinetics of CuS are more likely to result in the formation of large particles, and the existence of the large particles prolongs the diffusion path of lithium ions, which also makes it difficult to achieve effective recombination of CuS and the conductive network. Therefore, how to regulate the growth kinetics of CuS is limited while the CuS is uniformly compounded with the conductive matrixThe size of the particles is one of the key problems to be solved urgently for improving the cycling stability of the CuS/carbon composite material.
In recent years, ionic liquids, in particular, imidazolium ionic liquids, have been increasingly used in the synthesis of composite materials (chem. eur.j.,2012,18, 8230-8239; ACS appl.mater.interfaces,2017,9,8065-8074), which has a negligible vapor pressure, high stability and high designability, making them a green solvent of great interest. The ionic liquid is used as a composite medium, has the effects of reducing the particle size of a composite, stabilizing and reducing the stacking of layered objects and the like, thereby improving and enhancing the performance of the composite material and playing an important role in the synthesis of micro and nano materials. The metal-containing ionic liquid not only integrates the functions of a metal source, a nitrogen source, an assembly medium and a surface protective agent, but also has the special performance that the ionic liquid has better wettability with some carbon materials (Angew. chem., int.Ed.,2015,54, 231-. At present, the work of synthesizing a copper sulfide nano structure by using an ionic liquid containing copper metal as a precursor and compounding the copper sulfide nano structure with graphite oxide to construct a novel composite battery material is not reported yet.
Disclosure of Invention
According to one aspect of the application, the copper sulfide/nitrogen-doped graphite nanocomposite is provided, and the material is used as a lithium ion negative electrode material for assembling a battery, has excellent performance and is expected to be applied to a next generation lithium ion battery negative electrode material.
The invention relates to a copper sulfide composite material synthesized by using a copper-containing ionic liquid as a precursor, which is used for a lithium ion electrode material, and belongs to the technical field of energy storage.
The ionic liquid is used as an assembly medium and applied to the synthesis of a carbon-based composite material, so that the bonding strength between a metal chalcogenide nanostructure and a carbon material is improved, and the size of a metal chalcogenide is regulated, so that a high-performance lithium ion battery electrode material is obtained.
The application relates to a series of copper-containing halide ionic liquids [ C ]nMMIm]2[CuCl4]Methods for synthesizing novel composite materials for metal sources, nitrogen sources, assembly vehicles, and surface protectants and uses thereof. The application uses a liquid [ C ] containing metal ionsnMMIm]2[CuCl4]The composite material containing the ionic liquid is obtained by compounding the multifunctional precursor with graphite oxide and vulcanizing by a simple solvothermal method, and then the ionic liquid is removed by pyrolysis under the protection of mixed gas of hydrogen and nitrogen, so that the composite material of copper sulfide and nitrogen-doped graphite is obtained and is marked as CuS @ NG. The composite material prepared by the method is expected to be applied to the next generation of lithium ion battery cathode materials.
The copper sulfide/nitrogen-doped graphite nanocomposite is characterized in that copper sulfide with the average particle size of 10-20nm grows on the surface of nitrogen-doped graphite.
Specifically, in the compound, the sulfide forms nanoparticles with the size controllable between 10 nm and 20nm on the graphene conductive network, so that the compound is a uniform nano composite material, and the graphene can provide good functions of a charge transfer network and a material deformation support body.
Optionally, the weight percentage of copper sulfide in the copper sulfide/nitrogen-doped graphite nanocomposite is 10 wt% to 80 wt%.
Optionally, the upper limit of the weight percent of copper sulfide in the copper sulfide/nitrogen-doped graphite nanocomposite material is selected from 13.9 wt%, 18 wt%, 20 wt%, 23 wt%, 27.4 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, or 80 wt%; the lower limit is selected from 10 wt%, 13.9 wt%, 18 wt%, 20 wt%, 23 wt%, 27.4 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt% or 70 wt%.
Preferably, the weight percentage of copper sulfide in the copper sulfide/nitrogen-doped graphite nanocomposite is 18 wt% to 23 wt%.
Optionally, the copper sulfide/nitrogen-doped graphite nanocomposite is used as a lithium ion negative electrode material to assemble a battery, and the reversible charge and discharge capacity can reach 600mAh/g after 300 charge and discharge cycles at a current density of 200 mA/g.
Optionally, the copper sulfide/nitrogen-doped graphite nanocomposite can be used as a lithium ion negative electrode material to assemble a battery, and the capacity of the battery can still maintain 530mAh/g after 1000 charge and discharge cycles at a high current density of 2000 mA/g.
In another aspect of the present application, there is provided a method for preparing the copper sulfide/nitrogen-doped graphite nanocomposite material, comprising:
(1) stirring a mixture of an ionic liquid containing metal Cu and a graphite oxide dispersion liquid I, adding a sulfur source, stirring II, and heating for reaction to obtain a primary product;
(2) and (2) carrying out heat treatment on the primary product obtained in the step (1) to obtain the copper sulfide/nitrogen-doped graphite nano composite material.
Optionally, the ionic liquid containing metallic Cu in the step (1) is at least one selected from ionic liquids having a chemical formula shown in formula I:
[CnMMIm]2[CuX4]formula I
Wherein, CnMMIM is 1-n alkyl-2, 3-dimethyl imidazole, and n is 3-12;
x is at least one of Cl, Br and I;
the sulfur source is at least one selected from thiourea, sulfur powder, mercaptan and ammonium thiosulfate.
Optionally, when n ═ 12 in formula I, [ C ═ CnMMIm]2[CuCl4]Is a crystalline solid; when n is 3-11, [ C ]nMMIm]2[CuCl4]Is in liquid state.
Optionally, the ionic liquid containing metal Cu in the step (1) is [ CnMMIm]2[CuCl4](CnMMIm ═ 1-n alkyl-2, 3-dimethylimidazole; n-3-12).
Specifically, the ionic liquid containing the metal Cu can be used as a metal source, a nitrogen source, an assembly medium and a surface protective agent.
Alternatively, the ionic liquid containing metallic Cu can be obtained by prior art techniques.
Optionally, the method for obtaining the ionic liquid containing metallic Cu includes: mixing the ionic liquid and copper halide in a molar ratio, stirring, adding appropriate amount of water, and bathingHeating to mix them uniformly, then placing them into oven and drying so as to obtain the metal-containing ionic liquid [ CnMMIm]2[CuCl4]。
The cation of the ionic liquid is imidazole cation, and the anion of the ionic liquid is halogen chloride ion.
Optionally, the ionic liquid and copper source are present in a molar ratio of 2: 1.
optionally, the copper source comprises copper chloride dihydrate.
Optionally, the dispersant in the graphite oxide dispersion liquid is selected from at least one of ethanol and water.
Optionally, the concentration of the graphite oxide dispersion liquid is 0.5-2 mg/mL.
Alternatively, the graphite oxide is prepared using the Hummers method or a modified Hummers method.
Alternatively, X is selected from Cl or Br.
Optionally, the mass ratio of the ionic liquid containing metal Cu to the graphite oxide in the step (1) is 3: 1-44: 1;
the molar ratio of the added sulfur source to the ionic liquid containing the metal Cu is 3: 1-6: 1.
Optionally, the upper limit of the mass ratio of the ionic liquid containing the metal Cu to the graphite oxide is selected from 4: 1. 5: 1. 8: 1. 9.4: 1. 10: 1. 13.75: 1. 14.8: 1. 15: 1. 17.2: 1. 18: 1. 20: 1. 25: 1. 28: 1. 30: 1. 35: 1. 38: 1. 40: 1. 42: 1 or 44: 1; the lower limit is selected from 3: 1. 4: 1. 5: 1. 8: 1. 9.4: 1. 10: 1. 13.75: 1. 14.8: 1. 15: 1. 17.2: 1. 18: 1. 20: 1. 25: 1. 28: 1. 30: 1. 35: 1. 38: 1. 40: 1 or 42: 1.
optionally, the sulfur source is added in an amount such that the upper limit of the molar ratio of the sulfur source to the ionic liquid containing metallic Cu is selected from 4: 1. 5: 1. 6: 1; the lower limit is selected from 3: 1. 4: 1. 5: 1.
optionally, the stirring time of the stirring I in the step (1) is 1-4 hours.
Optionally, the stirring time of the stirring II in the step (1) is 0.5-2 hours.
Optionally, the reaction in step (1) is a solvothermal reaction.
Optionally, the heating reaction in step (1) has the following conditions: the heating temperature is 130-190 ℃; the heating time is 3-20 hours.
Optionally, the upper temperature limit of the heating reaction is selected from 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃ or 190 ℃; the lower limit is selected from 130 deg.C, 140 deg.C, 150 deg.C, 160 deg.C, 170 deg.C or 180 deg.C.
Optionally, the primary product subjected to the heat treatment in the step (2) is washed and dried.
Optionally, the washing is selected from at least one of water and ethanol.
Optionally, the drying temperature is 60-80 ℃; the drying time is 5-10 hours.
Optionally, the conditions of the heat treatment in step (2) are:
under the mixed atmosphere containing hydrogen and nitrogen, the heat treatment temperature is 200-250 ℃; the heat treatment time is 2-5 hours.
Optionally, the upper temperature limit of the heat treatment is selected from 210 ℃, 220 ℃, 230 ℃, 240 ℃ or 250 ℃; the lower limit is selected from 200 deg.C, 210 deg.C, 220 deg.C, 230 deg.C or 240 deg.C.
Optionally, the volume ratio of hydrogen to nitrogen in the mixed atmosphere is 1: 9;
the heating rate of the temperature rise to the heat treatment temperature is 1-5 ℃/min.
Specifically, the conditions of the heat treatment include: the heat treatment temperature is 200-250 ℃, the heating rate is 1-5 ℃/min, the heat treatment time is 2-5 hours, and the protective atmosphere is a hydrogen-nitrogen mixed gas, namely the volume ratio of hydrogen to nitrogen is 1:9, and (c) a mixed gas.
Optionally, the method comprises:
step a: obtaining a metal-containing ionic liquid;
the cation of the ionic liquid is imidazole cation, and the anion of the ionic liquid is halogen chloride ion;
step b: adding the metal-containing ionic liquid in the step a into the graphite oxide ethanol dispersion solution, and stirring;
step c: b, adding a sulfur source into the product obtained in the step b, and stirring;
step d: heating the product obtained in the step c for reaction, and reducing graphite oxide;
step e: d, washing and drying the product obtained in the step d;
step f: and e, carrying out heat treatment on the product obtained in the step e, and removing the ionic liquid and the redundant sulfur through pyrolysis to obtain the copper sulfide/nitrogen-doped graphite nanocomposite.
As one alternative embodiment, the method is a method for synthesizing a composite material by using a metal ion-containing liquid as a metal source, a nitrogen source, an assembly medium and a surface protective agent, and comprises the following steps:
step a 1: mixing an ionic liquid and copper chloride dihydrate according to a molar ratio of 2:1 for a period of time, adding a proper amount of water, heating in a water bath to mix uniformly, and then putting into an oven for drying to obtain a metal ion-containing liquid [ C ]nMMIm]2[CuCl4]Wherein, CnMMIM is 1-n alkyl-2, 3-dimethyl imidazole; when n is 12, [ C ]nMMIm]2[CuCl4]Is a crystalline solid; when n is 3-11, [ C ]nMMIm]2[CuCl4]Is in liquid state.
The cation of the ionic liquid is imidazole cation, and the anion of the ionic liquid is halogen chloride ion;
step b 1: b, adding the product obtained in the step a into a graphite oxide ethanol dispersion solution with a certain concentration synthesized in advance, and stirring for a period of time;
step c 1: b, adding a sulfur source into the product obtained in the step b, and stirring for a period of time;
step d 1: c, placing the product obtained in the step c into a drying oven at a certain temperature for reaction for a period of time, and reducing graphite oxide;
step e 1: d, centrifugally washing the product obtained in the step d with water and ethanol for three times respectively, and then drying the product in a vacuum drying oven at a certain temperature for a period of time;
step f 1: and e, carrying out heat treatment on the product obtained in the step e, and removing the ionic liquid and the redundant sulfur through pyrolysis to finally form the copper sulfide/nitrogen-doped graphite nano composite material.
The invention provides an ionic liquid [ C ] containing metallic coppernMMIm]2[CuCl4](CnMMIm ═ 1-n alkyl-2, 3-dimethylimidazole; n-3-12) as metal source, nitrogen source, assembly medium and surface protective agent, Cn represents that one side chain of the ionic liquid is n-alkyl, wherein n represents that the alkyl has n carbon atoms; by reacting [ CnMMIm]2[CuCl4]Adding into graphite oxide ethanol dispersion solution, and stirring for a period of time to obtain [ C ]nMMIm]+Bonds well with oxygen-containing functional groups on the graphite oxide. And further adding a sulfur source into the mixed solution, stirring for a period of time, and heating and annealing to obtain a series of composite materials based on graphite lamella loaded copper sulfide nano particles. In the composite, the sulfide forms nano particles with the size controllable between 10-20nm on the graphite conductive network, so that the composite is a uniform nano composite material, and the graphite can provide a good charge transport network. Notably, the copper sulfide composite material with ionic liquid participating in the synthesis is smaller than the nanoparticles with ionic liquid not participating in the synthesis; and the ionic liquid can form defective graphite carbon as a nitrogen source, so that the dissolution of sulfide formed in the charging and discharging process is better reduced, and the capacity is improved. In other synthetic methods, no reports have been made on the synthesis of copper sulfide nanoparticles and graphite oxide composites containing metal ion-containing liquids as precursors. It is worth mentioning that the ionic liquid can not only regulate and control the size of the copper sulfide nano-particles, but also induce the copper sulfide nano-particles and the carbon material to be better compounded because the ionic liquid and the oxygen-containing groups on the surface of the graphite oxide have strong electrostatic interaction.
The invention is realized by the following technical scheme: first through [ CnMMIm]2[CuCl4]Mixing with graphite oxide ethanol dispersion liquid, stirring to obtain mixture of ionic liquid and graphite oxide with electrostatic combination, adding sulfur source, stirring, heating for a period of time to obtain copper sulfide nanoparticles and copper sulfideAnd finally, carrying out thermal treatment on the composite structure of the original graphite sheet layer and pyrolyzing the ionic liquid to obtain the final copper sulfide/nitrogen-doped graphite nano composite material.
In yet another aspect of the present application, there is provided an electrode material for lithium ion batteries, comprising at least one of the copper sulfide/nitrogen-doped graphite nanocomposite material described above and the copper sulfide/nitrogen-doped graphite nanocomposite material prepared by the method described in any one of the above.
Optionally, the lithium ion battery electrode material is a lithium ion battery negative electrode material.
In still another aspect of the present application, there is provided a secondary battery electrode material, comprising at least one of the copper sulfide/nitrogen-doped graphite nanocomposite material described above and the copper sulfide/nitrogen-doped graphite nanocomposite material prepared by the method described in any one of the above.
The average particle diameter in the present application is a mass average particle diameter, i.e., the cumulative mass percentages above and below the particle diameter are equal (50% each).
The alkyl group in this application is a group formed by losing any one hydrogen atom on the molecule of the alkane compound.
The beneficial effects that this application can produce include:
1) in the nano composite material provided by the application, sulfide forms nano particles with the size controllable between 10 nm and 20nm on a graphite conductive network, so that the nano composite material is uniform, and graphite can provide a good charge transmission network;
2) in the preparation method of the nano composite material provided by the application, the ionic liquid can regulate and control the size of the copper sulfide nano particles, and meanwhile, the ionic liquid and oxygen-containing groups on the surface of graphite oxide have strong electrostatic interaction, so that the copper sulfide nano particles and a carbon material can be induced to be better compounded;
3) the nanocomposite provided by the application has excellent electrochemical performance when being used as a lithium ion negative electrode material for assembling a battery.
Drawings
FIG. 1 powder diffraction pattern of CuS @ NG-C6, experimental spectrum, and standard spectrum of example 1;
FIG. 2 XPS spectrum of CuS @ NG-C6 of example 1 (a) XPS spectrum of N of CuS @ NG-C6 (b);
FIG. 3 is a scanning electron micrograph (a) (b), a transmission electron micrograph (C), an HRTEM image (d) (e) and an elemental distribution map (f) of the CuS @ NG-C6 composite material of example 1;
FIG. 4. cyclic voltammogram of CuS @ NG-C6 of example 1;
FIG. 5 shows the capacity cycling results for CuS @ NG-C6 of example 1 at current densities of 200mA/g (a) and 2000mA/g (b).
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
In this application, [ C ] is selected6MMIm]2[CuCl4]As a medium, the ionic liquid cation is helpful to combine with an oxygen-containing functional pattern on the graphite oxide, and further introduces a sulfur source, and finally obtains the copper sulfide/nitrogen-doped graphite composite nano composite structure through heat treatment and annealing. In general, copper sulfide nanoparticles can show cluster morphology during the process of compounding with graphite oxide due to the reason that the faster nucleation and growth kinetics are more likely to lead to large particles, and the graphite oxide can show multi-layer agglomeration morphology. In the present compound due to [ C6MMIm]2[CuCl4]And the nano composite structure has the combined action with graphite oxide, so that the growth of nano particles is avoided, the surface of the nano particles is stabilized, the uniform nano structure is formed, the accumulation between layers of the graphite oxide is slowed down, and the nano composite structure with CuS nano particles uniformly loaded on a reduced graphite conductive network is finally formed.
Unless otherwise specified, the raw materials in the examples of the present application were all purchased commercially, and among them, references to the method for obtaining an ionic liquid containing metallic Cu: chemistry select,2018,3, 3731-.
Examples of the ionic liquids containing metallic copper [ C ]nMMIm]2[CuCl4](CnMMIm ═ 1-n alkyl-2, 3-dimethylimidazole; n-3-12), Cn represents an ionic liquid oneThe side chains are n-alkyl groups, where n represents an alkyl group having n carbon atoms.
References to methods for obtaining graphite oxide: J.am.chem.Soc.,1958,80, 1339-1339; ACS Nano,2010,4, 4806-.
The analysis method in the examples of the present application is as follows:
powder diffraction analysis was performed using a MiniFlex II X-ray powder diffractometer.
XPS spectroscopy was performed using ESCALB 250 Xi.
And performing scanning electron microscope analysis by using JSM-6700F.
Transmission electron microscopy analysis was performed using FEI Tecnai G2F 20.
Element distribution analysis (mapping) was performed using FEI Tecnai G2F 20.
Electrical performance analysis was performed using the CHI650E electrochemical workstation.
Example 1 with [ C ]6MMIm]2[CuCl4]Synthesis of CuS @ NG-C6 nanocomposite as medium
Step a: reference (chemistry select,2018,3,3731-3736) gave [ C6MMIm]2[CuCl4]: will [ C ]6MMIm]Cl and CuCl2·2H2O is mixed and stirred for 1 hour according to the molar ratio of 2:1, during which time a suitable amount of water is added and heated in a water bath to mix it evenly, and then the mixture is placed in a drying oven for drying overnight at 80 ℃.
Step b: adding the product in the step a (0.43g) into 1mg/mL of graphite oxide ethanol dispersion solution (50mL), and stirring for 4 hours; thiourea (0.34g) was then added and stirred for 2 hours and then placed in an oven at 140 ℃ for 3 hours.
Step c: c, centrifugally washing the product obtained in the step b with water and ethanol for three times respectively, and then drying the product in a vacuum drying oven at 60 ℃ for 10 hours;
step d: and c, carrying out heat treatment at 250 ℃ for 2 hours at the temperature rise rate of 1 ℃ per minute under the protection of hydrogen-nitrogen mixed gas (the volume ratio of hydrogen to nitrogen is 1:9) on the product obtained in the step c, pyrolyzing the ionic liquid of the multifunctional precursor in the product, and forming the final copper sulfide/nitrogen-doped graphite nano composite material in one step, wherein the mark is 2 #.
The differences in the preparation parameters for the other samples from sample 2# according to the above procedure are shown in table 1:
TABLE 1
The temperature of the solvent heat treatment is as follows: adding thiourea, and stirring to obtain the reaction temperature.
Example 2 sample structural characterization
The sample # 1 to the sample # 5 obtained in example 1 were characterized by X-ray powder diffraction, and the XRD spectra are shown in fig. 1, with the sample # 2 as a typical representative, and the XRD spectra of the sample # 1 and the sample # 3 to the sample # 5 are similar to those of fig. 1, i.e., the positions of diffraction peaks are substantially the same, and the peak intensities of different samples are slightly different. As can be seen from FIG. 1, the experimental spectrum corresponds well to the CuS standard spectrum, and has a carbon peak (002) crystal face. From this, it was confirmed that the obtained product was a composite of CuS and carbon.
The samples 1# to 5# in example 1 were characterized by raman spectroscopy, and the raman spectroscopy showed two characteristic peaks of reduced graphite and a characteristic peak of CuS, as typified by sample 2 #. The test results for sample # 1, sample # 3 to sample # 5 are similar to those described above.
The samples 1# to 5# obtained in example 1 were characterized by using an X-ray photoelectron spectroscopy (XPS), and the XPS spectra are represented by sample 2# and shown in fig. 2(a) and 2(b), and the XPS spectra of samples 1# and 3# to 5# are similar to fig. 2. As can be seen from fig. 2(a) and 2(b), the (a) diagram is a diagram of all elements contained in the final copper sulfide/nitrogen-doped graphite nanocomposite material, and the (b) diagram is a peak-divided diagram for N, demonstrating the successful doping of N into graphite.
Example 3 sample morphology characterization
The morphology of samples 1# to 5# in example 1 is characterized by a scanning electron microscope and a transmission electron microscope, and a scanning electron microscope image of the sample 2# is represented as shown in fig. 3(a) and 3(b), and it can be seen from the images that the morphology of the composite material is a loose nanosheet structure. The transmission electron microscope of sample 2# is shown in FIG. 3(c) -FIG. 3(e), from which it can be seen that CuS is supported on the graphite sheet layer, and the particle size of CuS is between 10-20 nm.
Fig. 3(f) is a mapping chart of sample 2# from which it can be seen that element C, N, O, S, Cu is uniformly distributed.
The test results of the other samples were similar to those of sample # 2.
Example 4 electrochemical Performance characterization
Carrying out electrochemical performance tests on samples 1# to 5# in the embodiment 1, typically sample 2 #; the cyclic voltammetry curve is tested, and the specific steps are as follows:
the negative electrode of the cell is prepared by mixing and coating active materials (sample No. 1 to sample No. 5 in example 1), acetylene black and a polyvinylidene fluoride binder in a mass ratio of 8:1:1 on copper foil, vacuum drying for 12 hours, and assembling into a CR2025 button cell in an oxygen-free environment for testing.
The first three cycles of cyclic voltammograms measured by the cell are shown in figure 4.
The cyclic voltammetry curve was tested on the electrochemical workstation of CHI650E under the following conditions: the voltage range is 1.0-3.0V, and the sweep rate is 0.1 mV/s.
The results are shown in FIG. 4. From fig. 4, it can be seen that the redox peaks of the cyclic voltammograms of the first three cycles coincide very well, indicating the very good stability of the material.
Carrying out capacity cycling tests on samples 1# to 5# in example 1, typically sample 2 #; the capacity cycling test is carried out on the test paper, and the specific steps are as follows:
the reversible charge-discharge capacity of the battery can reach 600mAh/g after 300 charge-discharge cycles under the current density of 200 mA/g; at a high current density of 2000mA/g, the capacity can still be maintained at 530mAh/g after 1000 cycles.
The capacity cycling results were tested on a LAND 2001A battery test system under conditions of a voltage range of 1.0-3.0V and a temperature of 25 ℃.
The results are shown in FIGS. 5(a) and 5 (b). It can be seen from fig. 5 that the battery has high capacity and good stability at both low and high current densities, indicating that the electrode material has superior battery performance.
The test results of the other samples were similar to those of sample # 2.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.
Claims (17)
1. A copper sulfide/nitrogen-doped graphite nanocomposite is characterized in that copper sulfide with an average particle size of 10-20nm grows on the surface of nitrogen-doped graphite;
the nitrogen source in the nitrogen-doped graphite is ionic liquid containing metal Cu.
2. The nanocomposite of claim 1, wherein the copper sulfide/nitrogen-doped graphite nanocomposite comprises 10 wt% to 80 wt% copper sulfide by weight.
3. The nanocomposite of claim 2, wherein the copper sulfide/nitrogen-doped graphite nanocomposite has a weight percent copper sulfide content of 18 wt% to 23 wt%.
4. The method of preparing the copper sulfide/nitrogen-doped graphite nanocomposite material of any one of claims 1 to 3, comprising:
(1) stirring a mixture of an ionic liquid containing metal Cu and a graphite oxide dispersion liquid I, adding a sulfur source, stirring II, and heating for reaction to obtain a primary product;
(2) and (2) carrying out heat treatment on the primary product obtained in the step (1) to obtain the copper sulfide/nitrogen-doped graphite nano composite material.
5. The method according to claim 4, wherein the ionic liquid containing metallic Cu in step (1) is at least one ionic liquid selected from ionic liquids having a chemical formula shown in formula I:
[CnMMIm]2[CuX4]formula I
Wherein, CnMMIM is 1-n alkyl-2, 3-dimethyl imidazole, and n is 3-12;
x is at least one of Cl, Br and I;
the sulfur source is at least one selected from thiourea, sulfur powder, mercaptan and thioacetamide.
6. The method according to claim 4, wherein the dispersant in the graphite oxide dispersion liquid is at least one selected from the group consisting of ethanol and water.
7. The method according to claim 4, wherein the concentration of the graphite oxide dispersion is 0.5 to 2 mg/mL.
8. The method of claim 5, wherein X is selected from Cl or Br.
9. The method according to claim 4, wherein the mass ratio of the ionic liquid containing metallic Cu to the graphite oxide in the step (1) is 3: 1-44: 1;
the molar ratio of the added sulfur source to the ionic liquid containing the metal Cu is 3: 1-6: 1.
10. the method according to claim 4, wherein the stirring I in the step (1) is carried out for 1-4 hours;
and (2) stirring time of the stirring II in the step (1) is 0.5-2 hours.
11. The method according to claim 4, wherein the conditions of the heating reaction in step (1) are as follows: the heating temperature is 130-190 ℃; the heating time is 3-20 hours.
12. The method according to claim 4, wherein the conditions of the heat treatment in step (2) are:
under the mixed atmosphere containing hydrogen and nitrogen, the heat treatment temperature is 200-250 ℃; the heat treatment time is 2-5 hours.
13. The method according to claim 12, wherein the volume ratio of hydrogen to nitrogen in the mixed atmosphere is 1: 9;
the heating rate of the temperature rise to the heat treatment temperature is 1-5 ℃/min.
14. The method of claim 13, wherein the method comprises:
step a: obtaining a metal-containing ionic liquid;
the cation of the ionic liquid is imidazole cation, and the anion of the ionic liquid is halogen chloride ion;
step b: adding the metal-containing ionic liquid in the step a into the graphite oxide ethanol dispersion solution, and stirring;
step c: b, adding a sulfur source into the product obtained in the step b, and stirring;
step d: heating the product obtained in the step c for reaction, and reducing graphite oxide;
step e: d, washing and drying the product obtained in the step d;
step f: and e, carrying out heat treatment on the product obtained in the step e, and removing the ionic liquid and the redundant sulfur through pyrolysis to obtain the copper sulfide/nitrogen-doped graphite nanocomposite.
15. A lithium ion battery electrode material comprising at least one of the copper sulfide/nitrogen-doped graphite nanocomposite material according to any one of claims 1 to 3, and the copper sulfide/nitrogen-doped graphite nanocomposite material prepared by the method according to any one of claims 4 to 14.
16. The lithium ion battery electrode material of claim 15, wherein the lithium ion battery electrode material is a lithium ion battery negative electrode material.
17. A secondary battery electrode material comprising at least one of the copper sulfide/nitrogen-doped graphite nanocomposite according to any one of claims 1 to 3, and the copper sulfide/nitrogen-doped graphite nanocomposite prepared by the method according to any one of claims 4 to 14.
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