CN115863578A - Sea anemone-shaped CoSe 2 Preparation method of composite material and application of sodium ion battery cathode - Google Patents
Sea anemone-shaped CoSe 2 Preparation method of composite material and application of sodium ion battery cathode Download PDFInfo
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Abstract
The invention provides an anemone-shaped CoSe 2 The preparation method of the composite material and the application of the negative electrode of the sodium-ion battery comprise the following steps: co (CO) is prepared by regulating and controlling hydrothermal synthesis conditions 3 ) 0.5 (OH)·0.11H 2 Adding the precursor into a Tris buffer solution for ultrasonic dispersion, adding dopamine into the precursor solution, and stirring at normal temperature to obtain a black precipitate-shaped isolate; washing with deionized water and ethanol, and oven drying to obtain Co (CO) 3 ) 0.5 (OH)·0.11H 2 O @ PDA; will dryUniformly mixing the substance and Se powder, and performing selenylation treatment to obtain CoSe with a sea anemone-shaped appearance 2 @ NC composite material. CoSe 2 The @ NC composite material is used as a negative electrode material of a sodium ion battery and is coated on 2Ag ‑1 The current density of the alloy can still maintain 214.6mAh g after being cycled for 100 times ‑1 The first coulombic efficiency of the specific capacity of the catalyst reaches 93.93 percent. The excellent sodium storage performance of the composite material can be attributed to the unique sea anemone-shaped structure of the composite material, the structure not only can provide more active sites for sodium storage, but also effectively relieves the volume expansion of the cathode material in the charging and discharging processes.
Description
Technical Field
The invention relates to the technical field of electrode materials, and particularly relates to an anemone-shaped CoSe 2 A preparation method of the composite material and application of a sodium ion battery cathode.
Background
In recent years, sodium ion batteries with promising development have received much attention due to the limited lithium resources and the high performance requirements for new electrode materials. However, the large-scale development of sodium ion batteries is hindered by the faster capacity fade during charge and discharge and the unstable cycling rate performance. Therefore, the search for suitable electrode materials is a problem to be solved. In the cathode material, cobalt diselenide has larger atomic layer spacing, can effectively improve the sodium storage capacity, and is a promising sodium ion cathode material. However, how to alleviate the volume expansion and structural pulverization of the material in electrochemical conversion becomes a difficult point and a focus of research. Yin prepared CoSe attached to carbon nanofibers 2 The test shows that the specific capacity of the particles is higher, and the cycling stability is obviously improved. Different groups have also demonstrated that CoSe was doped with N 2 The composite material can alleviate the capacity fade problem of long cycle processes. For example, yang et al demonstrate that N-doped carbon backbone composites exhibit very low capacity fade in the per-cycle test, which is in contrast to N-doped carbon matrices and CoSe that provide sodium storage sites 2 The strong binding energy between the particles is not very dense. Jo et al synthesized diamantane-like CoSe by multi-step heat treatment temperature design in cooperation with electrostatic spinning preparation method 2 Graphene nanofiber (N-CNT/rGO/CoSe) with nanocrystalline composite N-CNTs 2 NF). The unique structure of the flower-shaped golden hair grass provides a more convenient and faster channel for the transportation of sodium ions. The electrochemical test under the heavy current density of 10A/g shows that 10000 times of cycles are carried outN-CNT/rGO/CoSe after ring 2 The reversible capacity of NF reaches 264mAh/g, and high discharge capacity retention rate of 89% can be still realized after 100 th circulation. Zhao et al designed a nitrogen-doped carbon-based co-embedded TiO with ZIF-67 as a precursor 2 Coated layer of CoSe 2 Nanostructures (CoSe) 2 @NC@TiO 2 ). CoSe in nitrogen-doped carbon matrix 2 The nano-particles accelerate the transmission speed of sodium ions in the active material, and the sodium ions are subjected to a chemical performance test under the current density of 0.1A/g, the first charge-discharge capacity of the nano-particles is 520mAh/g, and after 200 cycles, the capacity retention rate is up to 78%.
Therefore, in the aspect of exploring the application of cobalt diselenide to the energy storage of the cathode material of the sodium-ion battery, firstly, consideration is given and the important key is to solve the problem of how to effectively relieve the volume expansion of the cathode material in the charging and discharging process. In summary, some researchers have adopted more complicated synthesis processes to prepare CoSe with different structures 2 A composite material. The composite material with a unique structure is prepared by an optimized process, more active sites are provided for sodium storage application, and the volume expansion of the negative electrode material in the charging and discharging process can be relieved to a high degree.
Disclosure of Invention
The invention constructs sea anemone-shaped CoSe 2 The preparation method of the composite material and the application of the sodium-ion battery cathode can effectively solve the problems in the application process.
The invention aims to provide sea anemone-shaped CoSe aiming at the defects of capacity attenuation, low first coulombic efficiency and the like in the prior art 2 A preparation method of the composite material and application of a sodium ion battery cathode. The method prepares the nitrogen-doped carbon layer-wrapped CoSe through simple hydrothermal synthesis and controllable gas-phase selenization steps 2 The composite material of the nano-particles has a unique sea anemone-shaped appearance. The ionic liquid is applied to a sodium ion battery cathode material, the initial coulombic efficiency is up to more than 90%, the cycle performance under a larger current density is obviously improved, the charge transfer resistance is smaller, and the electrochemical performance is excellent on the whole.
The invention is realized by the following steps:
the invention further provides a sea anemone-shaped CoSe 2 A method of making a composite material comprising the steps of:
s1, preparing and obtaining Co (CO) by regulating and controlling hydrothermal synthesis conditions 3 ) 0.5 (OH)·0.11H 2 And O precursor with unique sea anemone shape. Mixing Co (CO) 3 ) 0.5 (OH)·0.11H 2 Adding an O precursor into a buffer solution containing Tris with pH = 8.0-9.0, performing ultrasonic dispersion, and then performing ultrasonic dispersion according to Co (CO) 3 ) 0.5 (OH)·0.11H 2 The mass ratio of the O precursor to the dopamine is 0.8-1.9, dopamine is added into the solution, and the solution is stirred for 8-20 hours at normal temperature to obtain a black precipitate-shaped isolate;
s2, washing the obtained black precipitate-shaped separated substance for multiple times by using deionized water and ethanol, putting the washed separated substance into an oven, and keeping the temperature of 60-80 ℃ for 5-10 hours to obtain Co (CO) 3 ) 0.5 (OH)·0.11H 2 O@PDA；
S3, mixing Co (CO) 3 ) 0.5 (OH)·0.11H 2 Uniformly mixing O @ PDA and Se powder according to the mass ratio of 1 2 @NC。
The invention provides an anemone-shaped CoSe 2 The negative electrode active substance of the sodium ion battery made of the composite material is nitrogen-doped carbon-coated sea anemone-shaped CoSe 2 @ NC composite material, the nitrogen-doped carbon-coated modified sea anemone-shaped CoSe 2 The grain size of the @ NC composite material is 1-3 microns.
The invention has the beneficial effects that: coSe of the invention 2 The CoSe with the unique sea anemone-shaped structure is prepared from the composite material by a convenient low-cost hydrothermal synthesis method and a highly controllable selenization process 2 Material (CoSe) 2 @ NC). The material shows excellent electrochemical performance when being applied to a sodium ion battery cathode, the first coulombic efficiency is up to 93.93 percent, and the coulombic efficiency is 2A g -1 Current density of 2 after 100 cycles14.6mAh g -1 The specific capacity of (A). The composite material has excellent performance and a unique sea anemone-shaped structure, the special structure not only provides more active sites for realizing sodium storage application, but also effectively relieves the volume expansion of the cathode material in the charging and discharging process by the nitrogen-doped carbon coating layer on the surface of the material, so that the material has electrochemical performance with more application potential.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 shows Co (CO) provided by an embodiment of the present invention 3 ) 0.5 (OH)·0.11H 2 XRD characterization pattern of O precursor.
FIG. 2 shows Co (CO) provided by an embodiment of the present invention 3 ) 0.5 (OH)·0.11H 2 SEM image of O precursor.
FIG. 3 shows Co (CO) provided by an embodiment of the present invention 3 ) 0.5 (OH)·0.11H 2 SEM image of O @ PDA.
FIG. 4 is CoSe provided by embodiments of the present invention 2 XRD characterization pattern of @ NC.
FIG. 5 is CoSe provided by embodiments of the present invention 2 SEM picture of @ NC.
FIG. 6 is CoSe provided by embodiments of the present invention 2 At 0.1mV s -1 The scanning speed and the voltage window of the scanning electrode are 0.01 to 3.0V vs (Na/Na) + ) CV test curve of (2).
FIG. 7 shows CoSe provided by an embodiment of the present invention 2 And CoSe 2 The voltage window of the @ NC electrode material is 0.01-3.0V, and the current density is 200mA g -1 The charge-discharge curve of the first turn under the condition (1).
FIG. 8 is CoSe provided by embodiments of the present invention 2 And CoSe 2 @ NC at a current density of 2Ag -1 Cycling performance curve of 100 cycles under the conditions of (1).
FIG. 9 shows CoSe provided by an embodiment of the present invention 2 And CoSe 2 And the Nyquist map after @ NC cycle is shown, and the inset is a fitted equivalent circuit diagram.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The embodiment of the invention provides sea anemone-shaped CoSe 2 The preparation method of the composite material comprises the following steps:
s1, preparing and obtaining Co (CO) by regulating and controlling hydrothermal synthesis conditions 3 ) 0.5 (OH)·0.11H 2 And O precursor with unique sea anemone shape. Mixing Co (CO) 3 ) 0.5 (OH)·0.11H 2 Adding O precursor to Tris-containing solution at pH = 8.0-9.0Ultrasonic dispersion in buffer solution, then according to Co (CO) 3 ) 0.5 (OH)·0.11H 2 The mass ratio of the O precursor to the dopamine is 0.8-1.9, the mass of the added dopamine is closely related to the thickness of a nitrogen-doped carbon layer formed after gas-phase selenization, the thickness of the nitrogen-doped carbon layer is larger due to excessive addition of the dopamine, so that the cycle rate performance is influenced, and the nitrogen-doped carbon layer can not be coated due to too little dopamine; adding dopamine into the solution, and stirring for 8-20 h at normal temperature to obtain a black precipitate-shaped isolate;
s2, washing the obtained black precipitate-shaped separated substance for multiple times by using deionized water and ethanol, putting the washed separated substance into an oven, and keeping the temperature of 60-80 ℃ for 5-10 hours to obtain Co (CO) 3 ) 0.5 (OH)·0.11H 2 O@PDA；
S3, mixing Co (CO) 3 ) 0.5 (OH)·0.11H 2 O @ PDA and Se powder are uniformly mixed according to the mass ratio of 1 3 ) 0.5 (OH)·0.11H 2 O @ PDA is not fully selenized; if too much Se is added, residual molten Se simple substance is mixed in the CoSe of the target sample 2 @ NC, difficult to remove cleanly; placing the mixture in a tube furnace filled with Ar atmosphere, keeping the temperature at 350-450 ℃ for 2-6 h, controlling the heating rate at 1-5 ℃/min, performing selenization treatment, and finally obtaining CoSe 2 @ NC. The method can prevent a sample from being oxidized when the method is carried out in an inert atmosphere, and can better maintain the sea-sunflower-shaped morphology of the composite material within the temperature range.
As a further improvement, in step S1, the Co (CO) with unique sea anemone-like morphology 3 ) 0.5 (OH)·0.11H 2 The O precursor is obtained by the following method:
s11, adding a certain amount of cobalt acetate tetrahydrate into deionized water, stirring, adding urea after the cobalt acetate tetrahydrate is fully dissolved, stirring until a uniform mixed solution is formed, transferring the mixed solution into a 50ml reaction kettle, putting the reaction kettle into an oven, reacting for 5 hours at 100 ℃ to obtain a precipitate, centrifuging and washing the precipitate for multiple times by using the deionized water and alcohol, and drying the precipitate to obtain Co (CO) with a unique sea anemone-like morphology 3 ) 0.5 (OH)·0.11H 2 And O precursor for later use. Co (CO) 3 ) 0.5 (OH)·0.11H 2 The particle size and the shape of the O precursor can be adjusted by strictly regulating and controlling the parameter ratio of cobalt acetate tetrahydrate and urea. Preferably, in one embodiment, 1g to 1.5g of cobalt acetate tetrahydrate is added into 30ml of deionized water, 1g to 1.5g of urea is added after the cobalt acetate tetrahydrate is fully dissolved, the mixture is stirred to form a uniform mixed solution, then the uniform mixed solution is transferred into a 50ml reaction kettle, and the reaction kettle is placed into an oven to react for 5 hours at the temperature of between 100 and 120 ℃. The preferable addition amount of the cobalt acetate tetrahydrate and the urea is 1: when the amount of cobalt acetate tetrahydrate was 1g and the amount of urea was 1g as in example 1, the composite material formed had a unique sea anemone-like morphology. When the addition amounts of other ingredients such as cobalt acetate tetrahydrate and urea are 1, 4 and 1; the temperature range is 100-120 ℃, and the amount and the temperature of the added medicine are controlled to be important factors for obtaining the unique sea anemone-shaped morphology composite material.
As a further improvement, in the step S1, the pH of the buffer solution of Tris is 8.4-8.6. The alkalescent buffer solution is more beneficial to the self-polymerization process of the PDA subsequently so as to coat the PDA with Co (CO) 3 ) 0.5 (OH)·0.11H 2 O precursor surface.
As a further improvement, in step S1, the Co (CO) 3 ) 0.5 (OH)·0.11H 2 The method comprises the following steps of adding dopamine into a solution containing a precursor according to the mass ratio of 0.8-1.9:
according to Co (CO) 3 ) 0.5 (OH)·0.11H 2 And adding dopamine into the precursor-containing solution according to the mass ratio of 1.8. In step S2, washing the precipitate for several times by deionized water and ethanol, and drying at 70 deg.C for 8 hr to obtain Co (CO) 3 ) 0.5 (OH)·0.11H 2 O @ PDA for standby;
as a further improvement, in step S3, co (CO) is added 3 ) 0.5 (OH)·0.11H 2 O @ PDA and Se powderUniformly mixing the components according to the mass ratio of 1:
mixing Co (CO) 3 ) 0.5 (OH)·0.11H 2 And (2) uniformly mixing the O @ PDA and the Se according to the mass ratio of 1.
The embodiment of the invention further provides sea anemone-shaped CoSe 2 The negative electrode active substance of the sodium ion battery made of the composite material is nitrogen-doped carbon-modified sea anemone-shaped CoSe 2 @ NC composite material, coating PDA on the surface of precursor to form Co (CO) by the above steps 3 ) 0.5 (OH)·0.11H 2 O @ PDA, which is derived from PDA coated on the surface into nitrogen-doped carbon layer coated on CoSe after gas phase selenization 2 Forming modification on the surface of the nano-particles; the nitrogen-doped carbon-modified sea anemone-shaped CoSe 2 The grain size of the @ NC composite material is 1-3 microns. CoSe 2 The particle size of the particles of the @ NC composite material observed under SEM is different, and the particle size ranges from 1 micron to 3 microns and refers to the particle size after doping modification.
Example 1:
adding 1g of cobalt acetate tetrahydrate into 30ml of deionized water, adding 1g of urea after the cobalt acetate tetrahydrate is fully dissolved, stirring to form a uniform mixed solution, transferring the uniform mixed solution into a 50ml reaction kettle, putting the reaction kettle into an oven, and reacting for 5 hours at the temperature of 100 ℃. Washing the precipitate with deionized water and ethanol for several times, and drying to obtain Co (CO) with unique sea anemone shape 3 ) 0.5 (OH)·0.11H 2 And O precursor for later use. Preparing 100mL of buffer solution containing Tris, adjusting the pH value of the solution to 8.5 by controlling the addition amount of Tris, accurately weighing 0.1g of precursor to be dissolved in the buffer solution, ultrasonically dispersing for half an hour, adding 55mg of dopamine (PDA) according to the mass ratio of the precursor to the dopamine of 1.8Co(CO 3 ) 0.5 (OH)·0.11H 2 O @ PDA. Co (CO) to be produced 3 ) 0.5 (OH)·0.11H 2 And (2) uniformly mixing O @ PDA and Se powder according to the mass ratio of 1 2 Composite materials, i.e. CoSe 2 @ NC composite material.
Comparative example 1:
substantially similar to the examples, the comparative examples differ in that: co (CO) without dopamine coating treatment 3 ) 0.5 (OH)·0.11H 2 And uniformly mixing the O precursor and the Se powder according to the mass ratio of 1 2 A material.
Preparation and assembly of the electrode: the active material slurry was prepared from active material, conductive carbon (Super-P) and sodium carboxymethyl cellulose as binder in a ratio of 7:2:1, coating and grinding active substance slurry fully, coating the active substance slurry on a copper foil collector to prepare a working electrode, cutting the workpiece after vacuum drying and rolling, wherein the diameter of a circular pole piece is 12mm, a pure metal sodium sheet is taken as a counter electrode, and the button cell is assembled in a glove box filled with argon, and the diaphragm type is Celgard2325.
Structural characterization: the material phase analysis and the crystal structure analysis adopt a Bruker-D8-advanced type X-ray diffractometer (XRD), and the morphology and microstructure analysis of the sample adopt a Hitachi high and new SU8000 series super-resolution field emission Scanning Electron Microscope (SEM).
And (3) electrochemical performance characterization: the electrochemical performance of the material is characterized by adopting a blue battery test system (CT 3002 CA) to carry out constant-current charge-discharge test, and the voltage window of the electrochemical test is fixed at 0.01-3V. Both Cyclic Voltammetry (CV) and alternating impedance measurements (EIS) were performed by Shanghai Chenghua electrochemical workstation (CHI 660D) at a selected scan rate of 0.1mV s -1 The frequency range is 100 kHz-0.1 Hz.
Structural characterization:
precursor Co (CO) by XRD (FIG. 1) 3 ) 0.5 (OH)·0.11H 2 Characterizing the O crystal structure, and mixing the synthesized precursor spectrogram with Co (CO) 3 ) 0.5 (OH)·0.11H 2 And comparing the O standard cards, and finding that the positions corresponding to the characteristic diffraction peaks are consistent with the standard cards. SEM representation shows (figure 2), the prepared precursor presents a sea anemone shape, and the sizes of the sea anemone shape precursor are all about 1-3 micrometers.
Experimental example 1:
comparing the phase structures of the original and modified samples, coSe was first analyzed 2 And CoSe 2 The crystal structure of the @ NC composite material and the XRD spectrums of the @ NC composite material and the crystal structure are shown in figures 1 and 4. And CoSe 2 The standard cards are compared and can correspond to characteristic diffraction peaks at all positions in the spectrogram, and the characteristic peaks at 30.4 degrees, 34.2 degrees, 37.6 degrees, 43.7 degrees, 46.4 degrees, 51.7 degrees, 54.2 degrees, 56.4 degrees, 58.8 degrees, 63.4 degrees, 71.9 degrees, 73.9 degrees and 76.0 degrees in the spectrogram respectively correspond to CoSe 2 The (200), (210), (211), (220), (221), (311), (222), (230), (321), (400), (420), (421) and (332) crystal planes in (PDF # 09-0234) illustrate that pure-phase CoSe is successfully prepared by simple hydrothermal synthesis and a controllable gas-phase selenization method 2 A material. In addition, in CoSe 2 The XRD pattern of @ NC shows a wide diffuse peak near 20 degrees, which proves that CoSe 2 The presence of amorphous carbon in the @ NC composite.
Experimental example 2:
morphology structure of the product, applying SEM technique to Co (CO) 3 ) 0.5 (OH)·0.11H 2 O、Co(CO 3 ) 0.5 (OH)·0.11H 2 O@PDA、CoSe 2 And carrying out morphology characterization on the @ NC composite material. Fig. 3 is an SEM image of the precursor coated with dopamine hydrochloride, and comparing fig. 1, it is found that the surface of the precursor coated with dopamine is changed from original smooth to rough, but the sea anemone-like morphology of the whole material is still maintained. FIG. 5 is Co (CO) 3 ) 0.5 (OH)·0.11H 2 O @ PDA is converted into CoSe through controllable gas-phase selenization 2 The SEM picture of @ NC shows that the original sea anemone-shaped structure of the material can still be maintained after the material is carbonized, and fully shows that the carbon layer coated by the outer layer plays a good stabilizing role in the whole structureIt is sufficient to alleviate the volume change of the material to a large extent during charge-discharge cycles, thereby exhibiting excellent cycle stability. Meanwhile, due to the doping of dopamine-derived nitrogen elements, the wettability of the electrolyte can be increased in the contact process of the composite material and the electrolyte, a large number of active sites are provided for sodium storage, and the electronic conductance rate of the material is further increased.
And (3) electrochemical performance characterization:
the results of the above material structure and morphology characterization preliminarily confirm that the invention successfully prepares CoSe by simple hydrothermal synthesis and controllable gas phase selenization method 2 @ NC composite material. In order to research the improvement of electrochemical properties of the material by the sea anemone-shaped structure designed by the invention, coSe is used in the experiment 2 @ NC composite material and CoSe 2 And (4) carrying out comparison, respectively carrying out performance tests under the same experimental conditions from the aspects of cycle performance, constant current charging and discharging and alternating current impedance, and carrying out comparative analysis on results. Firstly, the electrochemical reaction process of the composite material in the charging and discharging cycle process is analyzed by using a cyclic voltammetry test (CV) method. FIG. 6 shows CoSe 2 The composite material electrode is at 0.1mV s -1 The scanning speed and the voltage window of the scanning electrode are 0.01 to 3.0V vs (Na/Na) + ) CV curve tested under the conditions of (a). On the initial CV cathode scan curve of the material, the peak at 1.04V corresponds to Na + With CoSe in the embedding material 2 Reacted and transformed into metal Co and Na 2 Se, accompanied by decomposition of the electrolyte and formation of Solid Electrolyte Interface (SEI). The peaks at 1.78 and 1.87V correspond to metallic Co nanocrystals and Na during anodic scanning 2 Reconversion of Se substrates to CoSe 2 . From the second circle, the reduction peak shifts towards the positive potential, which is caused by the large volume expansion of the composite material during the first circle cycle, and the change of the internal structure causes the change of the reduction peak position, which is also a common phenomenon of the transition metal compound in the sodium storage process. In addition, the comparison shows that the coincidence of the CV curves of the second circle and the third circle is better, and CoSe 2 The degree of polarization of the composite material is small, which indicates that the impedance of the modified composite material is obviously reduced, which is beneficial to Na + The process is rapidly de-intercalated in the electrochemical reaction, so that the cycling stability of the material is obviously improved.
Experimental example 3:
excellent electrochemical performance of the modified composite material, coSe 2 And CoSe 2 And carrying out constant current charge and discharge test on the @ NC composite material. FIG. 7 is CoSe 2 And CoSe 2 The voltage window of the @ NC composite material is 0.01-3.0V, and the current density is 200mAg -1 The first turn charge-discharge curve under the condition (1). Through the first cycle, coSe 2 The specific discharge capacity of the @ NC composite material is 359.3mAh g -1 The charging specific capacity is 337.7mAh g -1 The first coulombic efficiency was calculated to be as high as 93.93%, while under the same test conditions, coSe was obtained 2 The initial coulombic efficiency is only 45.83%, which shows that the nitrogen-doped carbon coating structure has great improvement effect on the cycle stability of the composite material, and the ultrahigh initial coulombic efficiency also shows that the material forms a very stable SEI film in the first cycle.
Experimental example 4:
the electrochemical performance of the composite material under a larger current density is subjected to cycle test on the material before and after modification. FIG. 8 is CoSe 2 And CoSe 2 @ NC composite Material at Current Density of 2Ag -1 Performance plots of 100 cycles under conditions. It can be found that the modified CoSe 2 After 100 cycles of the @ NC composite material, 214.6mAh g can still be kept -1 Without modified CoSe 2 The capacity of the material is quickly attenuated in the circulation process, and the specific capacity is attenuated to be close to zero after the material is circulated for 100 circles. Binding CoSe in SEM image 2 The @ NC composite material keeps a good sea anemone-shaped appearance, so that the sea anemone-shaped appearance has good structural stability, and meanwhile, the design of the nitrogen-doped carbon layer is beneficial to relieving volume expansion in a circulation process and slowing down the capacity attenuation rate. This unique sea anemone-like CoSe with carbon coating was further confirmed by the above cycle performance test 2 The @ NC composite material has excellent cycle stability.
Experimental example 5:
na in nitrogen-doped carbon layer pair material + DiffusionInfluence of kinetics on CoSe 2 And CoSe 2 The @ NC composite material is subjected to an alternating current impedance test within the frequency range of 100 kHz-0.1 Hz. FIG. 9 is CoSe 2 The Nyquist map of the electrode after the @ NC composite material is subjected to cycle test, and a small inset is a fitted equivalent circuit. It is clear that the Nyquist plots of the material before and after modification are both made up of a typical semicircle for the high frequency region and a diagonal line for the low frequency region. Wherein the high frequency region semi-circle corresponds to a charge transfer resistance (R) 2 ) And the slope of the low frequency region and Na + Diffused Warburg impedance (W) 1 ) It is related. The Nyquist map is fitted into an equivalent circuit diagram for analysis, coSe 2 And CoSe 2 Charge transfer resistance (R) of @ NC material 2 ) 473.7 Ω and 183.8 Ω, respectively, indicate that the interface impedance of the material is significantly reduced after the material is coated by the nitrogen-doped carbon layer, which is beneficial to promoting the transmission of electronic charges in the material, thereby showing more excellent electrochemical performance.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. Sea anemone-shaped CoSe 2 The preparation method of the composite material is characterized by comprising the following steps:
s1, preparing Co (CO) by hydrothermal synthesis 3 ) 0.5 (OH)·0.11H 2 Adding the precursor into a buffer solution containing Tris for ultrasonic dispersion, then adding dopamine into the solution, and stirring at normal temperature to obtain a black precipitate-shaped isolate;
s2, washing the separated substance by deionized water and ethanol, and drying to obtain Co (CO 3) 0.5 (OH). 0.11H2O @ PDA;
and S3, uniformly mixing Co (CO 3) 0.5 (OH). 0.11H2O @ PDA and Se powder, and performing selenization treatment to obtain the CoSe2@ NC composite material with the sea anemone-shaped appearance.
2. The method of preparing an anemone-like CoSe2 composite as claimed in claim 1, wherein in step S1, co (CO 3) 0.5 (OH). 0.11H2O precursor with unique anemone-like morphology is obtained by the following method:
s11, adding a certain amount of cobalt acetate tetrahydrate into deionized water, stirring, adding urea after the cobalt acetate tetrahydrate is fully dissolved, stirring until a uniform mixed solution is formed, transferring the mixed solution into a 50ml reaction kettle, putting the reaction kettle into an oven, reacting for 5 hours at 100 ℃ to obtain a precipitate, performing multiple centrifugal washing with the deionized water and alcohol, and finally drying to obtain a Co (CO 3) 0.5 (OH). 0.11H2O precursor with a sea anemone-shaped appearance.
3. The method of claim 1, wherein in step S1, the precursor is added to a buffer solution containing Tris and having a pH = 8.0-9.0, and subjected to ultrasonic dispersion.
4. The preparation method of the anemone-shaped CoSe2 composite material as claimed in claim 1, wherein in the step S1, dopamine is added into the solution according to the mass ratio of 0.5 (OH). 0.11H2O precursor of Co (CO 3) to 0.8-1.9;
5. the method for preparing the sea anemone-shaped CoSe2 composite material as claimed in claim 1, wherein in step S2, the obtained black precipitate-shaped isolate is washed with deionized water and ethanol for multiple times and then put into an oven, and the temperature is kept at 60-80 ℃ for 5-10 h to obtain Co (CO 3) 0.5 (OH). 0.11H2O @ PDA;
6. the preparation method of the sea anemone-shaped CoSe2 composite material as claimed in claim 1, wherein in the step S3, co (CO 3) 0.5 (OH). 0.11H2O @ PDA and Se powder are uniformly mixed according to a mass ratio of 1.
7. The preparation method of the anemone-shaped CoSe2 composite material as claimed in claim 6, wherein the mixture in step S3 is placed in a tube furnace filled with Ar atmosphere, the temperature is kept constant at 350-450 ℃ for 2-6 h, the heating rate is controlled at 1-5 ℃ and 1mi1, selenization is carried out, and finally the CoSe2@ NC composite material with the anemone-shaped appearance is obtained.
8. The application of the sodium ion battery cathode made of the sea anemone-shaped CoSe2 composite material is characterized in that the sodium ion cathode active substance is a nitrogen-doped carbon-modified sea anemone-shaped CoSe2@ NC composite material, and the particle size of the nitrogen-doped carbon-modified sea anemone-shaped CoSe2@ NC composite material is 1-3 micrometers.
9. The application of the negative electrode material of the sodium-ion battery as claimed in claim 6, wherein the negative electrode material of the sodium-ion battery has a coulombic efficiency of 93.93% for the first time, and can still maintain a specific capacity of 214.6mAh g < -1 > after being cycled for 100 times under a current density of 2Ag < -1 >.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211581819.2A CN115863578A (en) | 2022-12-09 | 2022-12-09 | Sea anemone-shaped CoSe 2 Preparation method of composite material and application of sodium ion battery cathode |
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