CN109037661B - Core-shell structure cobalt disulfide composite material and preparation method thereof - Google Patents
Core-shell structure cobalt disulfide composite material and preparation method thereof Download PDFInfo
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Abstract
The invention provides a preparation method of a core-shell structure cobalt disulfide composite material, which comprises the following steps: s1) mixing organic acid cobalt salt, an organic sulfur source, a glycol solvent, cetyl trimethyl ammonium bromide and an organic carbon source, and carrying out hydrothermal reaction to obtain an intermediate product; the organic sulfur source contains an amino group; s2) mixing the intermediate product with sulfur powder, and annealing in a protective atmosphere to obtain the core-shell structure cobalt disulfide composite material. Compared with the prior art, the core-shell structure cobalt disulfide composite material prepared by the invention has a good three-dimensional space structure, has an increased specific surface area and more reactive active sites, can also accommodate the volume change of cobalt disulfide during the process of sodium ion extraction, buffers the internal stress generated by the volume change, prevents the occurrence of substance pulverization phenomenon, and ensures the structural stability when the core-shell structure cobalt disulfide composite material is used as a sodium ion battery cathode material; the carbon layer on the surface enhances the electronic conduction capability and ensures the exertion of the excellent electrochemical performance of the cobalt disulfide.
Description
Technical Field
The invention belongs to the technical field of sodium ion batteries, and particularly relates to a core-shell structure cobalt disulfide composite material and a preparation method thereof.
Background
The sodium ion battery has the characteristics of rich sodium resource, low cost and the like, attracts the wide attention of researchers at home and abroad, and is considered as the best candidate for possibly replacing the lithium ion battery in the field of large-scale energy storage in future. In recent years, the research on sodium ion batteries has been advanced continuously, and the research systems are continuously abundant. However, sodium ions have larger ionic radius and slower kinetic rate, which become main factors restricting the development of sodium storage materials, and the development of high-performance sodium-inserted cathode materials is the key to improve the specific energy of sodium ion batteries and promote the application thereof.
Currently known negative electrode materials that can be used for sodium ion batteries are mainly carbon-based materials, alloy materials, elemental non-metals, metal oxides, organic compounds, and the like. The transition metal sulfide has abundant oxidation-reduction reaction sites and higher theoretical sodium storage capacity, so that high attention is paid to and development in the field of negative electrode materials of sodium-ion batteries.
Cobalt disulfide is a substance which is quite important in transition metal sulfide, cobalt metal ions can provide more binding points in electrochemical reaction, and also can play a role in electrocatalysis, so that the reaction energy level of the electrochemical reaction is reduced, the rapid combination and separation of ions are promoted, and the rapid sodium insertion and sodium removal reaction of a sodium ion battery is facilitated. Then, the conductivity of cobalt disulfide itself is low, and it can undergo huge volume change, or increase or shrink when it is deintercalated sodium ion, so when pure cobalt disulfide is used as sodium ion battery negative electrode material, there are two key defects that restrict its electric capacity to exert: firstly, the conductivity of cobalt disulfide is very poor, when the battery works, a large amount of electrons and ions are transferred and exchanged, but the cobalt disulfide cannot carry out the process quickly, the electrons conduct slowly, and the internal resistance of the battery is increased macroscopically, the polarization is serious, and the capacity is attenuated seriously; secondly, when the sodium ions are embedded, the volume of the cobalt disulfide can be increased by 300%, and when the sodium ions are separated, the volume of the cobalt disulfide can be reduced, so that the cobalt disulfide materials are extruded mutually due to severe volume change, internal stress concentration is caused, pulverization of the cobalt disulfide materials is finally caused, severe capacity attenuation occurs when the battery is subjected to long-cycle charge and discharge test, and the service life of the battery is shortened. Therefore, the cobalt disulfide used as the cathode material of the sodium ion battery needs to have special structure construction and reasonable surface layer design to exert the high sodium storage performance of the cobalt disulfide.
Chinese patent publication No. CN106558690A discloses a method for synthesizing a graphene-coated spherical cobalt disulfide composite material, in which graphene is used to coat cobalt disulfide particles, thereby improving the conductivity of the material, and the graphene can also provide a certain mechanical protection for the volume change of cobalt disulfide, and alleviate the internal stress change of the material. However, from the results reported in the patent, when the material is used for the negative electrode of a sodium ion battery, the material can provide a capacity of about 250mAh/g at a current density of 1000mA/g, and the capacity is only about 29.4 percent of the theoretical capacity of cobalt disulfide, and obviously cannot meet the requirement of a high-energy density battery. And the cycling stability can only keep 100 circles of charging and discharging, and obvious attenuation occurs in the subsequent cycling process, which indicates that the stability of the graphene-coated cobalt disulfide structure is not ideal.
Chinese patent publication No. CN105600745A discloses a method for preparing a cobalt disulfide/carbon nanofiber composite material. The carbon nanofiber is prepared by the electrostatic spinning method, and then the cobalt disulfide is loaded on the surface of the carbon nanofiber by a hydrothermal method, so that the cobalt disulfide/carbon nanofiber composite material is obtained. The carbon nanofiber has excellent conductivity, so that the defect of low conductivity of cobalt disulfide is overcome. But the structure can not solve the problem of internal stress concentration generated when the volume of the cobalt disulfide is greatly changed during charge and discharge cycles, which can cause the problem of poor cycle performance when the cobalt disulfide is used as a negative electrode material of a sodium ion battery. In addition, the preparation method is complex and has multiple processes, and the electrostatic spinning method is not beneficial to the mass production of the carbon nanofibers. In addition, the density of the cobalt disulfide composite material obtained by the invention is low, which is not beneficial to realizing the high energy-specific energy of the sodium-ion battery.
The existing patents and literature data are combined, and the problems of complex preparation process, poor long cycle performance of the battery and the like of the conventional cobalt disulfide sodium ion battery cathode material can be seen. Therefore, the design and preparation of a cobalt disulfide composite material with a special three-dimensional structure and excellent electrochemical properties are urgently needed.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a core-shell structure cobalt disulfide composite material with high specific capacity and good rate capability, and a preparation method thereof.
The invention provides a preparation method of a core-shell structure cobalt disulfide composite material, which comprises the following steps:
s1) mixing organic acid cobalt salt, an organic sulfur source, a glycol solvent, cetyl trimethyl ammonium bromide and an organic carbon source, and carrying out hydrothermal reaction to obtain an intermediate product; the organic sulfur source contains an amino group;
s2) mixing the intermediate product with sulfur powder, and annealing in a protective atmosphere to obtain the core-shell structure cobalt disulfide composite material.
Preferably, the step S1) is specifically:
A) mixing organic acid cobalt salt, an organic sulfur source and a glycol solvent to obtain a mixed solution;
B) and mixing the mixed solution, cetyl trimethyl ammonium bromide and an organic carbon source, and carrying out hydrothermal reaction to obtain an intermediate product.
Preferably, the mixing temperature in the step A) is 25-70 ℃; the mixing time is 5-60 min; the mixing temperature in the step B) is 25-70 ℃; the mixing time is 5-60 min.
Preferably, the organic acid cobalt salt is selected from one or more of cobalt oxalate tetrahydrate, cobalt formate dihydrate, cobalt propionate, cobalt carboxylate, cobalt diaminopropionate, cobalt isooctanoate and cobalt naphthoate; the organic sulfur source is selected from one or more of thiourea, ammonium thiocyanate, methionine, ethylene thiourea and thiosemicarbazide; the diol solvent is selected from one or more of methyl glycol, ethylene glycol, propylene glycol, hexylene glycol, pentanediol and cyclohexanediol; the organic carbon source is selected from one or more of glucose, mannose, fructose, galactose, xylose, crunchy candy, sucrose and trehalose.
Preferably, the mass ratio of the organic acid cobalt salt to the organic sulfur source is (2-8): 1; the mass ratio of the total mass of the organic acid cobalt salt and the organic sulfur source to the glycol solvent is 1: (50-150); the mass ratio of the hexadecyl trimethyl ammonium bromide to the organic carbon source to the organic acid cobalt salt is (1-5): (0.2-2): 1.
preferably, after the hydrothermal reaction in step S1), performing a centrifugal treatment to obtain an intermediate product; the rotating speed of the centrifugal treatment is 6000-12000 r/min; the time of the centrifugal treatment is 15-60 min.
Preferably, the temperature of the hydrothermal reaction is 100-200 ℃; the hydrothermal reaction time is 8-20 h; the temperature rise rate of the annealing treatment in the step S2) is 2-8 ℃/min; the heat preservation temperature of the annealing treatment is 300-800 ℃; the heat preservation time of the annealing treatment is 4-22 h.
Preferably, the mass ratio of the intermediate product to the sulfur powder is 1: (1-5).
The invention also provides a core-shell structure cobalt disulfide composite material, which comprises a core layer and a shell layer; the core layer is formed from stacked cobalt disulfide nanosheets; the core layer is a nitrogen-doped carbon layer.
The invention also provides application of the core-shell structure cobalt disulfide composite material as a sodium ion battery cathode material.
The invention provides a preparation method of a core-shell structure cobalt disulfide composite material, which comprises the following steps: s1) mixing organic acid cobalt salt, an organic sulfur source, a glycol solvent, cetyl trimethyl ammonium bromide and an organic carbon source, and carrying out hydrothermal reaction to obtain an intermediate product; the organic sulfur source contains an amino group; s2) mixing the intermediate product with sulfur powder, and annealing in a protective atmosphere to obtain the core-shell structure cobalt disulfide composite material. Compared with the prior art, the preparation method has the advantages that the cobalt salt of the organic acid and the organic sulfur source are selected as the cobalt source and the sulfur source respectively, the hexadecyl trimethyl ammonium bromide is used as the structure directing agent and the soft template to guide the cobalt disulfide to form a polyhedral structure under the specific hydrothermal condition, meanwhile, the organic carbon source can be statically adsorbed on the surface of the cobalt disulfide to form a carbon layer, and finally, the core-shell structure cobalt disulfide composite material can be obtained through carbonization and vulcanization; the polyhedral cobalt disulfide nanoparticles have larger specific surface area, are beneficial to exchange and transfer of sodium ions and electrons, are also beneficial to infiltration of electrolyte, and improve the electrochemical performance of the composite material; the core-shell structure cobalt disulfide composite material has a good three-dimensional space structure, has an increased specific surface area and more reactive active sites, can also accommodate the volume change of cobalt disulfide during the process of sodium ion extraction, buffers the internal stress generated by the volume change, prevents the occurrence of substance pulverization phenomenon, and ensures the structural stability when the cobalt disulfide composite material is used as a sodium ion battery cathode material; finally, the carbon layer on the surface of the core-shell structure cobalt disulfide composite material enhances the electronic conduction capability and ensures the exertion of the excellent electrochemical performance of cobalt disulfide.
The invention also provides a core-shell structure cobalt disulfide composite material, which comprises a core layer and a shell layer; the core layer is formed from stacked cobalt disulfide nanosheets; the core layer is a nitrogen-doped carbon layer. Compared with the prior art, the core-shell structure cobalt disulfide composite material provided by the invention is a polyhedral structure of a core-shell structure, has a good three-dimensional space structure, has an increased specific surface area and more reactive active sites compared with other structures, and the unique core-shell polyhedral structure can accommodate the volume change of cobalt disulfide during the process of sodium ion extraction, buffer the internal stress generated by the volume change, prevent the occurrence of substance pulverization phenomenon and ensure the structural stability when the cobalt disulfide composite material is used for a sodium ion battery cathode material; meanwhile, the carbon layer on the surface overcomes the defect of low conductivity of the cobalt disulfide, the electronic conduction capability is enhanced, and meanwhile, the carbon layer is firmly wrapped on the surface of the cobalt disulfide, so that the internal cobalt disulfide can be well protected, and the excellent electrochemical performance of the cobalt disulfide is ensured.
Drawings
FIG. 1 is a schematic diagram of the synthesis of a core-shell structure cobalt disulfide composite material provided by the invention;
fig. 2(a) is a scanning electron microscope image of the core-shell structure cobalt disulfide composite material obtained in example 1 of the present invention; (b) is a high-resolution scanning electron microscope image of the core-shell structure cobalt disulfide composite material obtained in the embodiment 2 of the invention;
FIG. 3 is a transmission electron microscope image of a core-shell structure cobalt disulfide composite material obtained in example 1 of the present invention;
FIG. 4 is a high-resolution transmission electron microscope image of the core-shell structure cobalt disulfide composite material obtained in example 2 of the present invention;
FIG. 5 is an XRD pattern of the cobalt disulfide composite material with core-shell structure obtained in example 2 of the present invention;
fig. 6 is a long-cycle charge-discharge diagram of a sodium ion battery using the core-shell cobalt disulfide composite material obtained in example 3 of the present invention as a negative electrode material.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of a core-shell structure cobalt disulfide composite material, which comprises the following steps: s1) mixing organic acid cobalt salt, an organic sulfur source, a glycol solvent, cetyl trimethyl ammonium bromide and an organic carbon source, and carrying out hydrothermal reaction to obtain an intermediate product; the organic sulfur source contains an amino group; s2) mixing the intermediate product with sulfur powder, and annealing in a protective atmosphere to obtain the core-shell structure cobalt disulfide composite material.
Referring to fig. 1, fig. 1 is a schematic synthetic diagram of a core-shell structure cobalt disulfide composite material provided by the present invention.
The preparation method is simple, good in repeatability and short in period. In the method, a cobalt disulfide phase can be formed only by hydrothermal self-assembly, and then the high-performance core-shell structure cobalt disulfide composite material can be obtained by annealing treatment. Compared with the traditional preparation process of the cobalt disulfide electrode material, the method has the advantages of simple process and high repeatability.
In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.
The organic acid cobalt salt is well known to those skilled in the art, and is not particularly limited, but in the present invention, one or more of cobalt oxalate, cobalt formate, cobalt propionate, cobalt carboxylate, cobalt diaminopropionate, cobalt isooctanoate, and cobalt naphthoate are preferred, and one or more of cobalt oxalate tetrahydrate, cobalt formate dihydrate, cobalt propionate, cobalt carboxylate, cobalt diaminopropionate, cobalt isooctanoate, and cobalt naphthoate are more preferred; the organic sulfur source is not particularly limited as long as it is an organic sulfur source containing amino groups, which is well known to those skilled in the art, and in the present invention, one or more of thiourea, ammonium thiocyanate, methionine, ethylenethiourea and thiosemicarbazide are preferable; the diol solvent is not particularly limited as long as it is well known to those skilled in the art, and in the present invention, one or more of methyl glycol, ethylene glycol, propylene glycol, hexylene glycol, pentylene glycol, and cyclohexanediol are preferable; the organic carbon source is not particularly limited as long as it is known to those skilled in the art, and in the present invention, it is preferably a saccharide compound, and more preferably one or more of glucose, mannose, fructose, galactose, xylose, crunchy candy, sucrose and trehalose.
According to the present invention, it is preferable to mix an organic acid cobalt salt, an organic sulfur source and a glycol solvent to obtain a mixed solution; the mass ratio of the organic acid cobalt salt to the organic sulfur source is preferably (2-8): 1, more preferably (2-6): 1, and preferably (3-5): 1, most preferably (3.8-4): 1; the mass ratio of the total mass of the organic acid cobalt salt and the organic sulfur source to the glycol solvent is preferably 1: (50 to 150), more preferably 1: (60-120), and more preferably 1: (70-100), most preferably 1: (80-90); the mixing method is preferably stirring, namely stirring is continuously carried out in the mixing process; the mixing temperature is preferably 25-70 ℃, more preferably 35-60 ℃, further preferably 40-50 ℃, and most preferably 45 ℃; the mixing time is preferably 5-60 min, more preferably 10-50 min, still more preferably 10-40 min, still more preferably 10-30 min, and most preferably 15-20 min.
Then mixing the mixed solution, the hexadecyl trimethyl ammonium bromide and the organic carbon source, preferably adding the hexadecyl trimethyl ammonium bromide and the organic carbon source into the mixed solution for mixing; the mass ratio of the hexadecyl trimethyl ammonium bromide to the organic carbon source to the organic acid cobalt salt is preferably (1-5): (0.2-2): 1, more preferably (1 to 4): (0.4-1.5): 1, and preferably (1-3): (0.5-1.2): 1, more preferably (1.4-2): (0.7-1): 1, most preferably (1.4 to 1.86): (0.7-1): 1; the mixing method is preferably stirring, namely stirring is continuously carried out in the mixing process; the mixing temperature is preferably 25-70 ℃, more preferably 35-60 ℃, further preferably 40-50 ℃, and most preferably 45 ℃; the mixing time is preferably 5-60 min, more preferably 10-50 min, still more preferably 20-40 min, and most preferably 30 min.
After mixing, carrying out hydrothermal reaction; the hydrothermal reaction is preferably carried out in a reaction kettle, and more preferably in a stainless steel reaction kettle; the temperature of the hydrothermal reaction is preferably 100-200 ℃, more preferably 150-200 ℃, and further preferably 180-200 ℃; the time of the hydrothermal reaction is preferably 8-20 h, more preferably 10-16 h, and further preferably 12-14 h.
After the hydrothermal reaction, preferably performing centrifugal treatment, separating a product, and preferably drying to obtain an intermediate product; the rotation speed of the centrifugal treatment is preferably 6000 to 12000r/min, more preferably 8000 to 12000r/min, still more preferably 9000 to 12000r/min, and most preferably 10000 r/min; the time of the centrifugal treatment is preferably 15-60 min, more preferably 15-50 min, still more preferably 15-30 min, and most preferably 20 min; the drying is preferably vacuum drying; the drying temperature is preferably 45-90 ℃, more preferably 45-80 ℃, further preferably 45-60 ℃ and most preferably 50 ℃; the drying time is preferably 3-12 h, more preferably 5-12 h, still more preferably 8-12 h, and most preferably 10 h.
And mixing the intermediate product with sulfur powder, and annealing in a protective atmosphere to obtain the core-shell structure cobalt disulfide composite material. The mass ratio of the intermediate product to the sulfur powder is preferably 1: (1-5), more preferably 1: (1-4), and more preferably 1: (1-3), most preferably 1: 3; the protective atmosphere is not particularly limited as long as it is known to those skilled in the art, and nitrogen and/or argon is preferable in the present invention; the heating rate of the annealing treatment is preferably 2-8 ℃/min, more preferably 3-7 ℃/min, still more preferably 4-6 ℃/min, and most preferably 5 ℃/min; the heat preservation temperature of the annealing treatment is preferably 300-800 ℃, more preferably 400-700 ℃, further preferably 500-700 ℃, and most preferably 600-700 ℃; the heat preservation time of the annealing treatment is preferably 4-22 h, more preferably 4-18 h, still more preferably 4-15 h, and most preferably 5-10 h.
According to the invention, organic acid cobalt salt and an organic sulfur source are respectively used as a cobalt source and a sulfur source, cetyl trimethyl ammonium bromide is used as a structure guiding agent and a soft template to guide cobalt disulfide to form a polyhedral structure under a specific hydrothermal condition, meanwhile, an organic carbon source can be statically adsorbed on the surface of the cobalt disulfide to form a carbon layer, and finally, the core-shell structure cobalt disulfide composite material can be obtained through carbonization and vulcanization, so that the preparation method is simple, the repeatability is good, and the period is short; the polyhedral cobalt disulfide nanoparticles have larger specific surface area, are beneficial to exchange and transfer of sodium ions and electrons, are also beneficial to infiltration of electrolyte, and improve the electrochemical performance of the composite material; the core-shell structure cobalt disulfide composite material has a good three-dimensional space structure, has an increased specific surface area and more reactive active sites, can also accommodate the volume change of cobalt disulfide during the process of sodium ion extraction, buffers the internal stress generated by the volume change, prevents the occurrence of substance pulverization phenomenon, and ensures the structural stability when the cobalt disulfide composite material is used as a sodium ion battery cathode material; finally, the carbon layer on the surface of the core-shell structure cobalt disulfide composite material enhances the electronic conduction capability and ensures the exertion of the excellent electrochemical performance of cobalt disulfide.
The invention also provides a core-shell structure cobalt disulfide composite material, which comprises a core layer and a shell layer; the core layer is formed from stacked cobalt disulfide nanosheets; the core layer is a nitrogen-doped carbon layer.
According to the invention, the particle size of the core-shell structure cobalt disulfide composite material is preferably 200nm, and the core-shell structure cobalt disulfide composite material consists of a core layer and a shell layer; the core layer is a polyhedron formed by stacking cobalt disulfide nanosheets; the shell layer is a nitrogen-doped carbon layer and wraps the surface of the polyhedral cobalt disulfide core layer, and the thickness of the carbon layer is preferably 0.4-1.5 nm.
The core-shell structure cobalt disulfide composite material provided by the invention is a polyhedral structure of a core-shell structure, has a good three-dimensional space structure, has an increased specific surface area and more reaction active sites compared with other structures, and the unique core-shell polyhedral structure can accommodate the volume change of cobalt disulfide during the process of sodium ion extraction, buffer the internal stress generated by the volume change of cobalt disulfide, prevent the occurrence of substance pulverization phenomenon and ensure the structural stability when the cobalt disulfide composite material is used for a sodium ion battery cathode material; meanwhile, the carbon layer on the surface overcomes the defect of low conductivity of the cobalt disulfide, the electronic conduction capability is enhanced, and meanwhile, the carbon layer is firmly wrapped on the surface of the cobalt disulfide, so that the internal cobalt disulfide can be well protected, and the excellent electrochemical performance of the cobalt disulfide is ensured.
The invention also provides application of the core-shell structure cobalt disulfide composite material as a sodium ion battery cathode material.
In order to further illustrate the present invention, the following describes in detail a core-shell structure cobalt disulfide composite material and a preparation method thereof, which are provided by the present invention, with reference to examples.
The reagents used in the following examples are all commercially available.
Example 1
Mixing 0.7g of cobalt oxalate tetrahydrate and 0.18g of thiourea, adding the mixture into a beaker filled with 70ml of glycol, and stirring in a water bath at the temperature of 45 ℃ for 15 min; then 1.3g of hexadecyl trimethyl ammonium bromide and 0.7g of glucose are weighed and added into the solution, and the solution is stirred and mixed evenly in a water bath at the temperature of 45 ℃ for 30 min.
Pouring the mixed and dissolved uniform solution into a stainless steel reaction kettle and sealing. Then the stainless steel reaction kettle is placed into a blowing oven with the temperature of 180 ℃ and is placed for 12 hours at constant temperature. And after the reaction, taking out the suspension in the reaction kettle. And then, carrying out centrifugal separation on the suspension, wherein the centrifugal rotating speed is set to 10000r/min, and the centrifugal time is 20 min. And putting the solid precipitate obtained by separation into a vacuum oven at 50 ℃, baking for 10h, and taking out.
2g of the dried powder was taken, mixed with 2g of sulfur powder, and placed in a tube furnace for annealing. And (3) argon is used as the atmosphere in the tubular furnace, the temperature rise rate of annealing treatment is 5 ℃/min, the heat preservation temperature is 600 ℃, and the heat preservation time is 5 hours, so that the core-shell structure cobalt disulfide composite material is finally obtained.
The core-shell structure cobalt disulfide composite material obtained in example 1 was analyzed by a scanning electron microscope to obtain a scanning electron microscope image, as shown in fig. 2. As can be seen from fig. 2(a), the core-shell structure cobalt disulfide composite material is a polyhedral structure, the diameter is about 200nm, and polyhedral nanoparticles are stacked one on another and have uniform size; the morphology of the single polyhedral core-shell structure cobalt disulfide composite material can be clearly seen from the high-resolution scanning electron microscope image of fig. 2 (b); the polyhedral core-shell structure cobalt disulfide composite material has a large specific surface area, is beneficial to exchange and transfer of sodium ions and electrons, is also beneficial to infiltration of electrolyte, and enhances the electrochemical performance of a negative electrode material.
The core-shell structure cobalt disulfide composite material obtained in example 1 was analyzed by a transmission electron microscope to obtain a transmission electron microscope image, as shown in fig. 3. The internal structure of the stack of wrinkled cobalt disulfide nanosheets can be seen more clearly in figure 3.
Example 2
0.7g of cobalt oxalate tetrahydrate and 0.18g of thiourea are mixed and added into a beaker filled with 70ml of glycol to be stirred in a water bath, wherein the temperature of the water bath is 45 ℃, and the stirring time is 15 min. Then 1.0g of hexadecyl trimethyl ammonium bromide and 0.5g of glucose are weighed and added into the solution, and the solution is stirred and mixed evenly in a water bath at the temperature of 45 ℃ for 30 min.
Pouring the mixed and dissolved uniform solution into a stainless steel reaction kettle and sealing. Then the stainless steel reaction kettle is placed into a blowing oven with the temperature of 180 ℃ and is placed for 12 hours at constant temperature. And after the reaction, taking out the suspension in the reaction kettle. And then, carrying out centrifugal separation on the suspension, wherein the centrifugal rotating speed is set to 10000r/min, and the centrifugal time is 20 min. And putting the solid precipitate obtained by separation into a vacuum oven at 50 ℃, baking for 10h, and taking out.
2g of the dried powder was taken, mixed with 4g of sulfur powder, and placed in a tube furnace for annealing. And (3) argon is used as the atmosphere in the tubular furnace, the temperature rise rate of annealing treatment is 5 ℃/min, the heat preservation temperature is 700 ℃, the heat preservation time is 10h, and finally the core-shell structure cobalt disulfide composite material is obtained.
The core-shell structure cobalt disulfide composite material obtained in example 2 was analyzed by a transmission electron microscope to obtain a high-resolution transmission electron microscope image, as shown in fig. 4. The crystal lattice trend and the crystal lattice spacing of the cobalt disulfide can be clearly distinguished from a high-resolution electron microscope image. Meanwhile, a nitrogen-doped carbon layer with the thickness of about 0.4-1.5nm can be clearly coated on the outermost layer of the polygonal cobalt disulfide. The figure further proves that the synthesized cobalt disulfide nano composite material is really in a core-shell structure, the carbon layer is uniform in thickness, the conductivity of cobalt disulfide is enhanced, and meanwhile, a protective layer can be provided when the cobalt disulfide is subjected to electrochemical reaction, so that the volume change of the cobalt disulfide is buffered, and the structural stability of the cobalt disulfide nano composite material is facilitated.
The core-shell structure cobalt disulfide composite material obtained in example 2 was analyzed by X-ray diffraction, and the XRD pattern thereof was obtained, as shown in fig. 5. From fig. 5, it can be found that the XRD diffraction peak of the sample perfectly corresponds to that given by the standard card, which fully indicates that the synthesized material is cobalt disulfide.
The core-shell structure cobalt disulfide composite material obtained in the example 2 is used as a negative electrode material of a sodium ion battery and is tested, and NaCF3SO3FIG. 6 shows a long-cycle charge-discharge diagram of a cell with electrolyte (sodium ions 1mol/L) and sodium metal as a counter electrode in DEGDME. Fig. 6 shows that the capacity of the electrode material is slightly attenuated after 600 times of cycle tests under the high current density of 1A/g, the capacity retention rate is more than 78%, the capacity can be kept at about 600mAh/g after 600 times of charge-discharge tests, and the structural stability of the polyhedral core-shell structure cobalt disulfide nano composite material and the high electrochemical performance of the polyhedral core-shell structure cobalt disulfide nano composite material applied to a sodium ion battery are shown.
Example 3
0.5g of cobalt formate dihydrate and 0.2g of methionine are mixed and added into a beaker filled with 70ml of glycol to be stirred in a water bath, wherein the temperature of the water bath is 45 ℃, and the stirring time is 15 min. Then 1.0g of hexadecyl trimethyl ammonium bromide and 0.5g of glucose are weighed and added into the solution, and the solution is stirred and mixed evenly in a water bath at the temperature of 45 ℃ for 30 min.
Pouring the mixed and dissolved uniform solution into a stainless steel reaction kettle and sealing. Then the stainless steel reaction kettle is placed into a blowing oven with the temperature of 180 ℃ and is placed for 12 hours at constant temperature. And after the reaction, taking out the suspension in the reaction kettle. And then, carrying out centrifugal separation on the suspension, wherein the centrifugal rotating speed is set to 10000r/min, and the centrifugal time is 20 min. And putting the solid precipitate obtained by separation into a vacuum oven at 50 ℃, baking for 10h, and taking out.
2g of the dried powder was taken, mixed with 4g of sulfur powder, and placed in a tube furnace for annealing. And (3) argon is used as the atmosphere in the tubular furnace, the temperature rise rate of annealing treatment is 5 ℃/min, the heat preservation temperature is 700 ℃, the heat preservation time is 10h, and finally the core-shell structure cobalt disulfide composite material is obtained.
Example 4
0.54g of cobalt propionate and 0.18g of ammonium thiocyanate are mixed and then added into a beaker filled with 60ml of glycol to be stirred in a water bath, wherein the temperature of the water bath is 45 ℃, and the stirring time is 15 min. Then 1.0g of hexadecyl trimethyl ammonium bromide and 0.5g of glucose are weighed and added into the solution, and the solution is stirred and mixed evenly in a water bath at the temperature of 45 ℃ for 30 min.
Pouring the mixed and dissolved uniform solution into a stainless steel reaction kettle and sealing. Then the stainless steel reaction kettle is placed into a blowing oven with the temperature of 180 ℃ and is placed for 12 hours at constant temperature. And after the reaction, taking out the suspension in the reaction kettle. And then, carrying out centrifugal separation on the suspension, wherein the centrifugal rotating speed is set to 10000r/min, and the centrifugal time is 20 min. And putting the solid precipitate obtained by separation into a vacuum oven at 50 ℃, baking for 10h, and taking out.
2g of the dried powder was taken, mixed with 3g of sulfur powder, and placed in a tube furnace for annealing. And (3) argon is used as the atmosphere in the tubular furnace, the temperature rise rate of annealing treatment is 5 ℃/min, the heat preservation temperature is 700 ℃, the heat preservation time is 10h, and finally the core-shell structure cobalt disulfide composite material is obtained.
Claims (8)
1. A preparation method of a core-shell structure cobalt disulfide composite material is characterized by comprising the following steps:
s1) mixing organic acid cobalt salt, an organic sulfur source, a glycol solvent, cetyl trimethyl ammonium bromide and an organic carbon source, and carrying out hydrothermal reaction to obtain an intermediate product; the organic sulfur source contains an amino group;
s2) mixing the intermediate product with sulfur powder, and annealing in a protective atmosphere to obtain the cobalt disulfide composite material with the core-shell structure;
the step S1) is specifically:
A) mixing organic acid cobalt salt, an organic sulfur source and a glycol solvent to obtain a mixed solution;
B) mixing the mixed solution, cetyl trimethyl ammonium bromide and an organic carbon source, and performing hydrothermal reaction to obtain an intermediate product;
the core-shell structure cobalt disulfide composite material comprises a core layer and a shell layer; the core layer is formed from stacked cobalt disulfide nanosheets; the shell layer is a nitrogen-doped carbon layer.
2. The method for preparing the compound of claim 1, wherein the temperature for mixing in the step A) is 25 to 70 ℃; the mixing time is 5-60 min; the mixing temperature in the step B) is 25-70 ℃; the mixing time is 5-60 min.
3. The method according to claim 1, wherein the organic acid cobalt salt is selected from one or more of cobalt oxalate tetrahydrate, cobalt formate dihydrate, cobalt propionate, cobalt carboxylate, cobalt diaminopropionate, cobalt isooctanoate, and cobalt naphthoate; the organic sulfur source is selected from one or more of thiourea, ammonium thiocyanate, methionine, ethylene thiourea and thiosemicarbazide; the diol solvent is selected from one or more of methyl glycol, ethylene glycol, propylene glycol, hexylene glycol, pentanediol and cyclohexanediol; the organic carbon source is selected from one or more of glucose, mannose, fructose, galactose, xylose, crunchy candy, sucrose and trehalose.
4. The preparation method according to claim 1, wherein the mass ratio of the organic acid cobalt salt to the organic sulfur source is (2-8): 1; the mass ratio of the total mass of the organic acid cobalt salt and the organic sulfur source to the glycol solvent is 1: (50-150); the mass ratio of the hexadecyl trimethyl ammonium bromide to the organic carbon source to the organic acid cobalt salt is (1-5): (0.2-2): 1.
5. the method according to claim 1, wherein the hydrothermal reaction in step S1) is followed by centrifugation to obtain an intermediate product; the rotating speed of the centrifugal treatment is 6000-12000 r/min; the time of the centrifugal treatment is 15-60 min.
6. The preparation method according to claim 1, wherein the temperature of the hydrothermal reaction is 100 ℃ to 200 ℃; the hydrothermal reaction time is 8-20 h; the temperature rise rate of the annealing treatment in the step S2) is 2-8 ℃/min; the heat preservation temperature of the annealing treatment is 300-800 ℃; the heat preservation time of the annealing treatment is 4-22 h.
7. The preparation method according to claim 1, wherein the mass ratio of the intermediate product to the sulfur powder is 1: (1-5).
8. The application of the core-shell structure cobalt disulfide composite material prepared by the preparation method of any one of claims 1 to 7 as a negative electrode material of a sodium ion battery.
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