CN113314715A

CN113314715A - Nickel sulfide composite material and preparation method and application thereof

Info

Publication number: CN113314715A
Application number: CN202110551779.6A
Authority: CN
Inventors: 刘芝婷; 陈逊杰; 蔡建钟; 郑文芝; 杨伟; 范浩森
Original assignee: Guangzhou University
Current assignee: Guangzhou University
Priority date: 2021-05-20
Filing date: 2021-05-20
Publication date: 2021-08-27
Anticipated expiration: 2041-05-20
Also published as: CN113314715B

Abstract

The invention belongs to the technical field of energy storage, and discloses a nickel sulfide composite material and a preparation method and application thereof. The nickel sulfide composite material has a core-shell structure and comprises an inner core and an outer shell, wherein the inner core comprises nickel sulfide, and the outer shell comprises a nitrogen-doped carbon shell. The shape is uniform and controllable, the structure is stable, and the crushing is not easy to occur; the nitrogen-doped carbon shell has better conductivity, and the shell formed by coating carbon can slow down the volume expansion of the nickel sulfide core in the long-term charge-discharge process, so that the stability of the material structure is ensured; the sodium ion battery cathode material can improve the battery capacity and the battery cycling stability. The preparation method provided by the invention adopts a three-step method, is simple, and can obtain the nickel sulfide composite material with uniform and controllable appearance. The nickel sulfide composite material provided by the invention can be applied to the preparation of batteries.

Description

Nickel sulfide composite material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of energy storage, and particularly relates to a nickel sulfide composite material and a preparation method and application thereof.

Background

In recent years, since energy consumption has become more severe, and the most popular lithium ion batteries at present have a large consumption of metallic lithium, researchers have been forced to search for the next generation of alkali metal ion batteries. Among them, the sodium ion battery is regarded as an expandable energy storage and conversion system with a development prospect, and has been receiving wide attention due to its low cost and abundant sodium resources.

In order to obtain satisfactory sodium ion battery performance, the negative electrode material is considered to be one of the most important. Metal sodium has a larger atomic radius than metal lithium, and thus, a conventional negative electrode material (e.g., a carbon matrix material, a transition metal oxide, etc.) applied to a lithium ion battery cannot achieve a higher capacity in a sodium ion battery. The search for a new generation of sodium ion battery cathode material becomes a research hotspot.

Transition Metal Sulfides (TMSs) are considered potential sodium ion storage candidates due to their high theoretical capacity. However, the use of transition metal sulfides is also frequently frustrated, mainly due to two aspects: (1) transition metal sulfides, although having better electrical conductivity than transition metal oxides, are still unsatisfactory for their application in sodium ion batteries; (2) since the transition metal sulfide is charged and discharged in a sodium ion battery in a "conversion mechanism" manner, the material is expanded and pulverized, failing to exhibit good stability performance and high capacity over a long period of cycles.

Therefore, it is highly desirable to provide a nickel sulfide material that has a stable structure, high capacity, and high cycling stability as a negative electrode for sodium ion batteries.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the nickel sulfide composite material provided by the invention has a stable structure, is not easy to break, is used as a negative electrode material of a sodium ion battery, and has high capacity and strong cycle stability.

In a first aspect, the present invention provides a nickel sulphide composite material.

Specifically, the nickel sulfide composite material has a core-shell structure and comprises an inner core and an outer shell, wherein the inner core comprises nickel sulfide, and the outer shell comprises a nitrogen-doped carbon shell.

Preferably, the diameter of the inner core is 1-1.5 μm, and the thickness of the outer shell is 100-150 nm.

The invention provides a preparation method of a nickel sulfide composite material.

Specifically, the preparation method of the nickel sulfide composite material comprises the following steps:

(1) dissolving nickel acetate and a surfactant in alcohol, and carrying out solvothermal reaction to obtain a precursor;

(2) dispersing the precursor prepared in the step (1) in a tris (hydroxymethyl) aminomethane solution, adding dopamine hydrochloride, reacting, and filtering to obtain a precipitate to prepare a coating body;

(3) and (3) mixing the cladding body prepared in the step (2) with sulfur, and calcining to prepare the nickel sulfide composite material.

The nickel sulfide composite material is prepared by solvothermal, in-situ polymerization and calcination. Firstly, carrying out ester exchange reaction on nickel acetate and alcohol (methanol), and meanwhile, taking a surfactant as a soft template to assemble the ultrathin two-dimensional nanosheets into a unique and uniform spherical precursor (such as hydroxymethyl nickel hydroxide); carrying out surface in-situ polymerization by utilizing dopamine hydrochloride to form a coating body; finally, a nickel sulfide composite material with a core-shell structure is generated in the carbonization/vulcanization (calcination) process, nitrogen doping and carbon coating are realized, the nitrogen-doped carbon shell greatly improves the electrochemical performance of the material, and on one hand, compared with a pure carbon shell, the nitrogen-doped carbon shell has better electric conductivity; on the other hand, in the core-shell structure, the carbon shell can slow down the volume expansion of the nickel sulfide core in the long-term charge-discharge process, so that the stability of the material structure is ensured, and the cycle life of the material is prolonged.

In the preparation method, dopamine hydrochloride is adopted for in-situ polymerization coating of the precursor, so that a coating layer with uniform thickness is formed on the surface of the precursor, and after calcination treatment, the carbon coating layer is uniform, stable and not easy to break. The inventor researches and discovers that if other nitrogen-containing organic matters are adopted to replace dopamine hydrochloride, uniform coating cannot be achieved, a finally formed carbon coating layer is not uniform, and the phenomenon of core-shell breaking is easy to occur.

Preferably, in the step (1), the concentration of the nickel acetate is 0.02-0.2mol L-¹。

Preferably, in step (1), the surfactant is cetyltrimethylammonium bromide or polyvinylpyrrolidone. Cetyl trimethyl ammonium bromide or polyvinylpyrrolidone is beneficial to inducing ultrathin nanosheets to assemble into flower balls in the solvothermal reaction to form a precursor.

Preferably, in step (1), the alcohol is methanol.

Preferably, in step (1), the amount of the substance of the surfactant is 0.5% to 8% of the amount of the substance of the nickel acetate; further preferably, in step (1), the amount of the substance of the surfactant is 1% to 5% of the amount of the substance of the nickel acetate.

Preferably, in the step (1), the temperature of the solvothermal reaction is 100-200 ℃, and the time of the solvothermal reaction is 12-60 h; further preferably, in the step (1), the temperature of the solvothermal reaction is 120-200 ℃, and the time of the solvothermal reaction is 12-48 h.

Preferably, in the step (2), the precursor is dispersed by using a Tris (hydroxymethyl) aminomethane solution (Tris solution) with a concentration of 0.005-0.020 mol-¹. The tris (hydroxymethyl) aminomethane solution not only can disperse the precursor, but also can adjust the pH of the dispersion liquid, thereby being beneficial to the subsequent coating of dopamine hydrochloride.

Preferably, in step (2), the reaction temperature is room temperature (e.g., 10-35 ℃), and the reaction time is 8-36 h.

Preferably, in the step (3), the mass ratio of the clad body to the sulfur is (1-3): (1-3); further preferably, in the step (3), the mass ratio of the clad body to the sulfur is (1-2): (1-2).

Preferably, in step (3), the calcination process is performed in a nitrogen atmosphere.

Preferably, in the step (3), the calcining temperature is 300-600 ℃, and the calcining time is 1-6 h; further preferably, in the step (3), the calcination temperature is 300-500 ℃, and the calcination time is 1-4 h.

In a third aspect, the invention provides the use of said nickel sulphide composite material.

The nickel sulfide composite material is applied to the preparation of batteries.

A battery negative electrode material comprises the nickel sulfide composite material.

A sodium ion battery negative electrode material comprises the nickel sulfide composite material.

A battery comprising the nickel sulfide composite.

Compared with the prior art, the invention has the following beneficial effects:

(1) the nickel sulfide composite material provided by the invention has a core-shell structure and comprises an inner core and an outer shell, wherein the inner core comprises nickel sulfide, and the outer shell comprises a nitrogen-doped carbon shell. The shape is uniform and controllable, the structure is stable, and the crushing is not easy to occur; the nitrogen-doped carbon shell has better conductivity, and the shell formed by coating carbon can slow down the volume expansion of the nickel sulfide core in the long-term charge-discharge process, so that the stability of the material structure is ensured; the sodium ion battery cathode material can improve the battery capacity and the battery cycling stability.

(2) The preparation method provided by the invention adopts a three-step method, is simple, and can obtain the nickel sulfide composite material with uniform and controllable appearance.

Drawings

FIG. 1 is an SEM image of a nickel sulfide composite material prepared in example 1;

FIG. 2 is a NiS obtained in comparative example 1₂SEM images of microspheres;

FIG. 3 shows the nickel sulfide composite obtained in example 1 and the NiS obtained in comparative example 1₂XRD pattern of microspheres;

FIG. 4 is a plot of the voltammetric cycling profile of a cell made using example 1;

fig. 5 is a graph of rate performance of batteries manufactured in application example 1 and comparative example 2;

fig. 6 is a graph showing cycle characteristics of the batteries manufactured in application example 1 and comparative example 2.

Detailed Description

In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples are given for illustration. It should be noted that the following examples are not intended to limit the scope of the claimed invention.

The starting materials, reagents or apparatuses used in the following examples are conventionally commercially available or can be obtained by conventionally known methods, unless otherwise specified.

Example 1

A preparation method of a nitrogen-doped carbon-coated nickel sulfide composite material with a core-shell structure comprises the following steps:

(1) by 0.02mol L-¹Uniformly dissolving nickel acetate tetrahydrate and 2% (relative to the molar mass of nickel acetate tetrahydrate) hexadecyl dimethyl ammonium bromide in a methanol solvent, transferring the solution into a polytetrafluoroethylene lining, putting the lining into a hydrothermal outer kettle, fixing and sealing the lining, and carrying out solvothermal reaction for 48 hours at 180 ℃. Cooling to room temperature after the reaction is finished, centrifugally washing for three times by using ethanol, and drying for 12 hours in vacuum at the temperature of 60 ℃ to obtain a precursor, namely hydroxymethyl nickel hydroxide Ni (OH) (OCH)₃)。

(2) Prepare 100mL of 0.01mol L-¹Accurately weighing 100mg of the precursor, and uniformly dispersing the precursor in the Tris solution by using ultrasound. Subsequently, 50mg of dopamine hydrochloride was weighed into the above Tris solution under stirring, and the solution was reacted for 24 hours with stirring (in situ polymerization treatment). Finally centrifuging, washing, vacuum drying at 60 deg.C for 12h to obtain coated body, and recording as Ni (OH) (OCH)₃)@PDA。

(3) 0.2g of sublimed sulphur was mixed with 0.1g of Ni (OH) (OCH)₃) The @ PDA is loaded into a small porcelain boat, the two ends of the tube furnace are respectively placed, and the sublimed sulfur is close to the air inlet end. In a nitrogen atmosphereCalcining the mixture for 2 hours at the temperature of 350 ℃ to finally obtain the nickel sulfide composite material (marked as NiS) with the core-shell structure_x@NC)。

Application example 1

The nickel sulfide composite material prepared in example 1 was used as a negative electrode material of a sodium ion battery, and a battery was prepared.

The method comprises the following specific steps: the nickel sulfide composite material (NiS) obtained in example 1 was used_x@ NC) and acetylene black and polyvinylidene fluoride according to the mass ratio of 7: 2:1, grinding the mixture by taking N-methyl pyrrolidone as a solvent to prepare slurry, coating the slurry on the surface of copper foil, and drying the copper foil in a vacuum drying oven at the temperature of 60 ℃ for 12 hours to prepare the sodium ion battery negative plate.

Taking a metal sodium sheet as a positive electrode sheet and taking the concentration as 1mol L-¹Sodium hexafluorophosphate is used as electrolyte, ethylene glycol dimethyl ether is used as solvent, and the button cell is assembled by dropping a proper amount of electrolyte into the positive plate shell, the positive plate, the elastic sheet, the gasket, the diaphragm, the negative plate and the negative plate shell in a glove box. The process is conventional and will not be described in great detail.

Comparative example 1

This comparative example provides a NiS₂The microspheres were not subjected to dopamine hydrochloride in situ polymerization treatment as compared to example 1.

Specifically, NiS of this comparative example₂The preparation method of the microsphere comprises the following steps:

(1) by 0.02mol L-¹The concentration of the method is that nickel acetate tetrahydrate and 2 percent (relative to the molar weight of the nickel acetate tetrahydrate) of surfactant are uniformly dissolved in a methanol solvent, the solution is transferred into a polytetrafluoroethylene lining, the lining is put into a hydrothermal outer kettle for fixing and sealing, and the solvent thermal reaction is carried out for 48 hours at 180 ℃. Cooling to room temperature after the reaction is finished, centrifugally washing for three times by using ethanol, and drying for 12 hours in vacuum at the temperature of 60 ℃ to obtain a precursor, namely hydroxymethyl nickel hydroxide Ni (OH) (OCH)₃)。

(2) 0.2g of sublimed sulfur and 0.1g of Ni (OH) (OCH) are mixed according to the mass ratio of 2:1₃) Loading into small porcelain boats, respectively placing at two ends of the tube furnace, and allowing sublimed sulfur to approach the air inlet end. Calcining the mixture for 2 hours at 350 ℃ in a nitrogen atmosphere to finally obtain NiS₂And (3) microspheres.

Comparative example 2

The vulcanized composite material prepared in the comparative example 1 was used as a negative electrode material of a sodium ion battery, and a battery was prepared.

The method comprises the following specific steps: NiS obtained in comparative example 1₂The mass ratio of the microspheres to acetylene black and polyvinylidene fluoride is 7: 2:1, grinding the mixture by taking N-methyl pyrrolidone as a solvent to prepare slurry, coating the slurry on the surface of copper foil, and drying the copper foil in a vacuum drying oven at the temperature of 60 ℃ for 12 hours to prepare the sodium ion battery negative plate.

Product effectiveness testing

(1) And (3) morphology characterization:

for the nickel sulfide composite material (NiS) obtained in example 1_x@ NC) and NiS from comparative example 1₂The microspheres were analyzed by scanning electron microscopy. Nickel sulfide composite material (NiS)_x@ NC) is shown in fig. 1. In FIG. 1, a and b represent the nickel sulfide composite material (NiS) at different resolutions respectively_x@ NC). As can be seen from FIG. 1, the nickel sulfide composite (NiS) provided by the present invention_x@ NC) has a uniform three-dimensional spherical microscopic morphology, and meanwhile, the spherical particles have a core-shell structure and comprise a core and a shell, wherein the particle size of the core is 1-1.5 mu m, and the thickness of the shell is 100-150 nm.

NiS₂The morphology of the microspheres is shown in FIG. 2, wherein a and b in FIG. 2 represent NiS at different resolutions respectively₂SEM images of microspheres. As can be seen from a comparison of FIG. 1, NiS without nitrogen doping and carbon coating treatment₂The microspheres have no core-shell structure and are broken, which indicates that the microspheres are easy to break at high temperature in the vulcanization process.

For the nickel sulfide composite material (NiS) obtained in example 1_x@ NC) and NiS from comparative example 1₂The microspheres were subjected to X-ray diffraction analysis. FIG. 3 shows a nickel sulfide composite (NiS)_x@ NC) and NiS₂XRD patterns of the microspheres, the curves in FIG. 3 represent nickel sulfide (PDF #02-1298), nickel disulfide (PDF #11-0099) and NiS respectively₂Microsphere and nickel sulfide composite (NiS)_x@ NC). Nickel sulfide composite material (NiS)_x@ NC) with the PDF #02-1298 card of nickel sulfide and the PDF #11-0099 card of nickel disulfide, and the success of the invention in preparing the nickel sulfide microsphere with the core-shell structure can be demonstrated by combining with figure 1.

(2) And (3) electrochemical performance testing:

electrochemical performance tests were performed on the batteries prepared in example 1 and comparative example 2, respectively. FIG. 4 shows the results of applying the battery obtained in example 1 at 0.1 mV. s-¹Voltammetric cyclic plot of time, with potential on the abscissa and current on the ordinate. As can be seen from fig. 4, the cell prepared in application example 1 has a reduced peak with a higher intensity at 1.24V in the first cyclic voltammetry scan, which corresponds to the formation of SEI film. In the following scan, the two pairs of oxidation/reduction peaks, 1.72V/1.44V and 1.96V/0.91V, correspond to the conversion reaction

And the de-intercalation of sodium ions. In addition, as can be seen from fig. 4, the curve shapes of the second circle and the third circle are basically consistent, which shows that the material has better reversibility and strong cycle stability.

FIG. 5 is a graph showing rate characteristics of batteries manufactured in application example 1 and comparative example 2, in which the abscissa is a cycle number and the ordinate is a specific capacity, and the curves in FIG. 5 represent the batteries manufactured in application example 1 (NiS), respectively_x@ NC) and comparative example 2 (NiS)₂) At a current density of 1-5A g-¹Graph of rate performance. As can be seen from FIG. 5, the values are 0.1, 0.2, 0.5, 1, 2A g-¹At a current density of (2), nickel sulfide composite material (NiS)_x@ NC) having 401.5, 389.6, 375.6, 346.8, 318.9mA h g-¹High specific discharge capacity. Even when the current density is 5A g-¹Still has 297.2mA h g-¹Specific discharge capacity of (2). And the material was not carbon-coated, the battery (NiS) obtained in comparative example 2₂) At 0.1-5A g-¹The discharge specific capacity under the current density is only 243.2, 201.6, 198.6, 184.3, 176.2mA h g-¹All lower than the battery prepared in application example 1, indicating that NiS₂The performance of the microsphere as the battery cathode material is far inferior to that of a nickel sulfide composite material (NiS)_x@NC)。

Finally, cycling stability is a significant impediment to battery applications, particularly sodium ion batteries. Therefore, the present invention also investigated the cycle stability of the batteries obtained in application example 1 and comparative example 2 at 1A g-¹The cycle test was performed at the current density of (1). FIG. 6 shows application example 1 (NiS)_x@ NC) and comparative example 2 (NiS)₂) And (3) a cycle performance graph of the prepared battery, wherein the abscissa is a cycle number, and the ordinate is specific capacity. As can be seen from FIG. 6, after 100 cycles, application example 1 (NiS)_x@ NC) prepared battery still shows higher specific discharge capacity (368.4mA h g^-1) And remains at 98.68% of the first turn. And by NiS not coated with carbon₂Battery prepared from microspheres is 1A g^-1After circulating for 100 circles under the current density of (1), only 148.6mA h g is shown^-1The retention rate of the discharge specific capacity of the lithium ion battery is only 56 percent; and, application example 1 (NiS)_x@ NC), the specific capacity was reduced by 50%. Therefore, the NiS can be effectively improved by compounding through carbon coating treatment₂The micro-morphology of the microspheres is more beneficial to ion and electron transmission, so that the specific capacity and the cycling stability of the microspheres are improved.

The charge-discharge mechanism of transition metal sulfides in sodium ion batteries is similar to that in lithium ion batteries, mainly through conversion reactions. Although the transition metal sulfides have a higher theoretical capacity (e.g., NiS: about 590mA hr g)^-1，NiS₂: about 879mA hr g^-1) However, the conversion reaction causes a large volume expansion effect, resulting in pulverization of the material and further a sharp drop in capacity. In addition, during the charging and discharging processes, transition metal sulfides often generate intermediate products (polysulfide), and the intermediate products are easily dissolved in the electrolyte, so that the battery capacity is reduced. Therefore, the nickel sulfide composite material with the core-shell structure is formed by coating the nitrogen-doped carbon shell, and the nickel sulfide composite material canTo improve the electrochemical performance of the material from at least three aspects: firstly, the nitrogen-doped carbon shell can effectively improve the diffusion rate of electrons and sodium ions, thereby improving the rate capability of the material; secondly, the nitrogen-doped carbon shell is used as a protective layer, and the microscopic morphology and structure of the material are protected by inhibiting the inevitable volume expansion of the material caused in long-term circulation; and thirdly, the nitrogen-doped carbon shell is used as an isolating layer, so that direct contact between an intermediate product and electrolyte is reduced. Thus, compare NiS₂Material, NiS_x@ NC shows higher rate capability and cycle stability capability.

Claims

1. A nickel sulfide composite material is characterized by having a core-shell structure and comprising an inner core and an outer shell, wherein the inner core comprises nickel sulfide, and the outer shell comprises a nitrogen-doped carbon shell.

2. The nickel sulfide composite material of claim 1, wherein the diameter of the inner core is 1-1.5 μm and the thickness of the outer shell is 100-150 nm.

3. Method for the preparation of a nickel sulphide composite material according to claim 1 or 2, characterized in that it comprises the following steps:

4. The method according to claim 3, wherein the surfactant in step (1) is cetyltrimethylammonium bromide or polyvinylpyrrolidone.

5. The preparation method as claimed in claim 3, wherein in the step (1), the temperature of the solvothermal reaction is 100-200 ℃, and the time of the solvothermal reaction is 12-60 h.

6. The production method according to claim 3, wherein in the step (3), the mass ratio of the clad body to the sulfur is (1-3): (1-3).

7. The preparation method as claimed in claim 3, wherein in the step (3), the calcination temperature is 300-600 ℃ and the calcination time is 1-6 h.

8. Use of a nickel sulphide composite material according to claim 1 or 2 in the manufacture of a battery.

9. A battery negative electrode material, characterized by comprising the nickel sulfide composite material according to claim 1 or 2.

10. A battery comprising the nickel sulfide composite material according to claim 1 or 2.