KR102304760B1 - Nitrogen-doped molybdenum sulfide/carbon composite for sodium ion battery of core-shell structure, manufacturing method thereof and sodium ion battery comprising the same - Google Patents

Abstract

The present invention relates to a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure, a method for producing the same, and a sodium ion battery comprising the same, and more particularly, a polymer obtained from a polymer precursor through an acid catalytic reaction into a shell part Thus, a nitrogen-doped molybdenum sulfide/carbon composite having a uniform particle size can be prepared by coating the surface of the nitrogen-doped molybdenum sulfide, which is the core part, and heat-treating it. In addition, the nitrogen-doped molybdenum sulfide/carbon composite for sodium ion battery of the present invention controls the particle size of the carbonized porous carbon as a shell part of the composite. It is possible to prevent the growth of the solid electrolyte interfacial layer on the surface of the anode, and to suppress the occurrence of electrolyte side reactions, thereby improving the electrochemical properties such as charge/discharge capacity, lifespan and rate of the battery.

Description

Nitrogen-doped molybdenum sulfide/carbon composite for core-shell structure sodium ion battery, manufacturing method thereof, and sodium ion battery comprising the same SODIUM ION BATTERY COMPRISING THE SAME}

The present invention relates to a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure, a manufacturing method thereof, and a sodium ion battery including the same.

As the demand for secondary batteries grows, from small electronic devices such as smartphones and laptops to hybrid electric vehicles (HEVs) and electric vehicles (EVs), large-capacity power storage systems (Energy storage system, ESS) interest in energy storage devices is growing in many fields. In particular, although research on lithium-ion batteries as an energy source for ESS is being actively conducted, research on next-generation secondary batteries that can replace them is attracting new attention due to problems such as regional localization of lithium resources and rapid price fluctuations. Among them, sodium ion batteries, which are abundant in the earth's crust and utilize sodium resources that are cheaper than lithium resources, are spotlighted as next-generation secondary batteries to replace lithium ion batteries.

However, due to the sodium ion radius about 1.3 times larger than that of lithium ion, graphite, a commercial anode for lithium ion batteries, cannot be applied to sodium ion batteries, so the development of an anode material for sodium ion batteries is necessary. As an alternative to anode materials for sodium ion batteries, antimony (Sb) and tin (Sn) are metal materials with charge/discharge behavior by alloying with sodium ions, and have high theoretical capacities of 660 and 847 mAh/g, respectively. For this reason, many studies are being conducted.

On the other hand, as another high-capacity negative electrode material for sodium ion batteries, molybdenum sulfide (MoS ₂ ) or antimony sulfide (Sb ₂ S ₃ ) has not only high theoretical capacities of 670, 946 mAh/g by conversion reaction with sodium ions, but also It has the advantage of better stability than antimony and tin. However, all alloy-based and conversion-based high-capacity anode materials have improved battery life stability in relation to the problem of extreme volume expansion that occurs during charge/discharge behavior, the growth of the solid electrolyte interphase (SEI) layer on the material surface, and electrolyte side reactions. It still has problems that greatly hinder it.

In an attempt to improve these problems, Chunzhong Li's research team at East China University in China announced a study in 2017 _{that synthesized nanosheet-shaped MoS 2} and applied it as a cathode material for sodium ion batteries. Xiangeng Meng's research team announced a study in 2018 _{that synthesized MoS 2} in the shape of nanotubes and applied it as a cathode material for sodium ion batteries. Despite these efforts, previous studies have a problem of increasing the process cost because a complex process is required, and MoS ₂ still has extreme volume expansion during charging/discharging even in sodium ion batteries, so it has a large limitation as a high-capacity anode material. There is this.

Conventional Korean Patent Application Laid-Open No. 2016-041625 discloses a method for manufacturing _{MoS 2 / carbon nanocomposite by forming molybdenum disulfide (MoS 2} ) precursor particles in a hydrochloric acid solution and then performing heat treatment while flowing hydrocarbon gas. However, in the case of the above document, a separate hydrochloric acid solution is mixed in the process of forming the complex, and the manufacturing process is complicated because a hydrocarbon gas must be flowed, and it is difficult to control the particle size _{of the MoS 2 / carbon nanocomposite with the hydrocarbon gas.} is agglomerated, so there is a limitation in manufacturing a composite having a uniform and uniform size.

Therefore, it is urgent to solve problems such as the problem of extreme volume expansion of the existing anode materials for sodium ion batteries, the growth of the SEI layer on the surface of the anode, and the electrolyte side reaction, and research and development for new anode materials is necessary to improve these problems. am.

Korea Patent Publication No. 2016-041625

In order to solve the above problems, an object of the present invention is to provide a method for manufacturing a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure having a simple manufacturing process and a uniform particle size. .

Another object of the present invention is to provide a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure with improved electrical conductivity and structural stability.

In addition, the present invention provides a negative electrode material for sodium ion batteries comprising the nitrogen-doped molybdenum sulfide / carbon composite in which the occurrence of electrolyte side reactions is suppressed while preventing the volume expansion of the negative electrode active material and the growth of the SEI layer on the surface of the negative electrode. do.

Another object of the present invention is to provide a sodium ion battery comprising the anode material having improved electrochemical properties such as charge/discharge capacity, lifespan and rate.

The object of the present invention is not limited to the object mentioned above. The objects of the present invention will become more apparent from the following description, and will be realized by means and combinations thereof described in the claims.

The present invention comprises the steps of preparing a mixture by mixing a molybdenum precursor, a precursor containing sulfur and nitrogen, a polymer precursor, and a solvent; preparing a nitrogen-doped molybdenum sulfide/polymer complex by reacting the mixture at 60 to 90° C. for 14 to 32 hours; and heat-treating the nitrogen-doped molybdenum sulfide/polymer composite to prepare a nitrogen-doped molybdenum sulfide/carbon composite. do.

The molybdenum precursor is MoCl _{5 ,} MoF ₆ , MoCl ₆ , MoO ₃ , Mo(CO) ₆ , Na ₂ MoO ₄ .2H ₂ O and (NH ₄ )6Mo ₇ O ₂₄ .4H ₂ O One selected from the group consisting of may be more than

The precursor containing sulfur and nitrogen may be at least one selected from the group consisting of thioacetamide, thiourea, and aminothiophenol.

The polymer precursor may be at least one selected from the group consisting of furfural, aniline, acetylene, pyrrole, and thiophene.

The solvent may be at least one selected from the group consisting of ethanol, propanol, methanol, butanol, pentanol, hexanol, acenonitrile, ethyl acetate, diethyl ether, trichloroethylene and diglomethane.

In the step of preparing the mixture, the molybdenum precursor, the precursor containing sulfur and nitrogen, and the polymer precursor may be mixed in a molar ratio of 2.2: 7.7: 0.1 to 0.8: 7.7: 1.5.

In the step of preparing the nitrogen-doped molybdenum sulfide/carbon composite, the heat treatment may be performed at 700 to 1000° C. under a reducing atmosphere for 30 minutes to 4 hours.

The reducing atmosphere may be performed in at least one inert gas selected from the group consisting of hydrogen gas, argon gas, helium gas, and nitrogen gas.

The nitrogen-doped molybdenum sulfide/carbon composite may include a core including a nitrogen-doped molybdenum sulfide compound; and a shell portion including carbonized porous carbon, wherein the core portion may have a core-shell structure in which all or at least a portion of a surface of the core portion is covered by the shell portion.

The nitrogen-doped molybdenum sulfide/carbon composite may have an average particle size of 400 to 800 nm.

The nitrogen-doped molybdenum sulfide/carbon composite may include 0.1 to 10% by weight of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite.

The nitrogen-doped molybdenum sulfide/carbon composite may have a specific surface area (BET) of 3 to 20 m ² /g and an average pore size of 10 to 40 nm.

In the step of preparing the mixture, the molybdenum precursor, the precursor containing sulfur and nitrogen, and the polymer precursor are mixed in a molar ratio of 2.1: 7.7: 0.2 to 1: 7.7: 1.3, preparing the nitrogen-doped molybdenum sulfide/carbon composite In the heat treatment is performed at 750 to 890 ° C. for 1 to 3 hours under a reducing atmosphere, the nitrogen doped molybdenum sulfide / carbon composite has an average particle size of 480 to 700 nm, and the nitrogen doped molybdenum sulfide / carbon composite is nitrogen Contains 0.5 to 8% by weight of carbon based on the total weight of the doped molybdenum sulfide/carbon composite, and the nitrogen-doped molybdenum sulfide/carbon composite has a specific surface area (BET) of 7 to 13 m ² /g, and an average pore size It may be 20-32 nm.

In the step of preparing the mixture, the molybdenum precursor, the precursor containing sulfur and nitrogen, and the polymer precursor are mixed in a molar ratio of 2: 7.7: 0.3 to 1.3: 7.7: 1, the molybdenum precursor is MoCl ₅ , and the sulfur and nitrogen are mixed The precursor comprising is thioacetamide, the polymer precursor is furfural, and in the step of preparing the nitrogen-doped molybdenum sulfide/carbon composite, the heat treatment is performed at 780 to 850 ° C. under a reducing atmosphere for 1.5 to 2.5 hours, and the The nitrogen-doped molybdenum sulfide/carbon composite has an average particle size of 500 to 600 nm, and the nitrogen-doped molybdenum sulfide/carbon composite contains 1 to 5% by weight of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite, , The nitrogen-doped molybdenum sulfide/carbon composite may have a specific surface area (BET) of 8.5 to 12 m ² /g, and an average pore size of 26 to 30 nm.

On the other hand, the present invention is a core comprising a nitrogen-doped molybdenum sulfide compound; and a shell portion comprising carbonized porous carbon, wherein the core portion has a core-shell structure in which all or at least a portion of the surface is covered by the shell portion. /Provides a carbon complex.

The nitrogen-doped molybdenum sulfide/carbon composite may have an average particle size of 400 to 800 nm.

The nitrogen-doped molybdenum sulfide/carbon composite may have a specific surface area (BET) of 3 to 20 m ² /g and an average pore size of 10 to 40 nm.

The nitrogen-doped molybdenum sulfide/carbon composite may include 0.1 to 10% by weight of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite.

The present invention also provides an anode material for a sodium ion battery comprising the nitrogen-doped molybdenum sulfide/carbon composite.

The present invention also provides a sodium ion battery comprising the negative electrode material.

The present invention uses a polymer obtained from a polymer precursor through an acid catalytic reaction as a shell part, coats the surface of nitrogen-doped molybdenum sulfide as a core part, and heat-treats it to crystallize nitrogen-doped molybdenum sulfide, and simultaneously carbonize the polymer to have a uniform particle size A nitrogen-doped molybdenum sulfide/carbon composite having

In addition, in the nitrogen-doped molybdenum sulfide/carbon composite for sodium ion battery according to the present invention, the volume expansion of the negative electrode active material and the growth of the solid electrolyte interfacial layer on the surface of the negative electrode during the charging and discharging process by controlling the particle size of the carbonized porous carbon as the shell part It can be prevented, and it is possible to increase the life of the battery by suppressing the occurrence of an electrolyte side reaction.

In addition, the nitrogen-doped molybdenum sulfide/carbon composite for sodium ion battery according to the present invention has a simple manufacturing process, and when applied as a negative electrode material for sodium ion battery by improving the stability of the core-shell structure, electricity such as charge/discharge capacity, lifespan and rate Chemical properties can be improved.

The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a schematic diagram schematically illustrating a method for preparing a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure of the present invention.
2 is a scanning electron microscope (FE _{) of the MoS 2} , N-MoS ₂ and N-MoS ₂ /C composite prepared in Comparative Example 1 (a), Comparative Example 2 (b) and Example 1 (c) of the present invention. -SEM) and transmission electron microscope (TEM) analysis results are shown.
3 is an X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis _{of the N-MoS 2} /C composite prepared in Example 1 and Comparative Examples 1 and 2 of the present invention _{, MoS 2} and N-MoS ₂ This is a graph showing the results.
4 is a graph showing the surface area (BET) analysis results of _{the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2 of the present invention.
5 is a graph showing the thermogravimetric analysis (TGA) results of _{the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2 of the present invention.
6 is a one-time charge/discharge evaluation result of a sodium secondary battery prepared using the _{N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2 of the present invention. This is the graph shown.
_{7 is a N-MoS 2} /C composite prepared in Example 1 and Comparative Examples 1 and 2 of the present invention _{, MoS 2} and N-MoS ₂ Charging according to the number of charge/discharge cycles of a sodium secondary battery prepared using N-MoS 2 It is a graph showing the dose evaluation result.
8 is a graph showing the evaluation results of the rate characteristics of the sodium secondary battery prepared using the _{N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2 of the present invention. .

Hereinafter, the present invention will be described in more detail by way of one embodiment.

The present invention relates to a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure, a manufacturing method thereof, and a sodium ion battery including the same. Specifically, the present invention comprises the steps of preparing a mixture by mixing a molybdenum precursor, a precursor containing sulfur and nitrogen, a polymer precursor, and a solvent; preparing a nitrogen-doped molybdenum sulfide/polymer complex by reacting the mixture at 60 to 90° C. for 14 to 32 hours; and heat-treating the nitrogen-doped molybdenum sulfide/polymer composite to prepare a nitrogen-doped molybdenum sulfide/carbon composite. do.

1 is a schematic diagram schematically illustrating a method for preparing a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure of the present invention. Referring to FIG. 1, a nitrogen-doped molybdenum sulfide/polymer composite is prepared by mixing a molybdenum precursor with a precursor containing sulfur and nitrogen in a solvent containing a polymer precursor and reacting it for an appropriate temperature and time. Next, a process for preparing a nitrogen-doped molybdenum sulfide/carbon composite by heat-treating the composite at a high temperature under a reducing atmosphere for a certain time is shown. At this time, the nitrogen-doped molybdenum sulfide/carbon composite uses nitrogen-doped molybdenum sulfide as a core part and carbonized porous carbon as a shell part, so that all or at least a part of the surface of the core part is covered by the shell part It has a core-shell structure show that

In the step of preparing the mixture, the molybdenum precursor is MoCl _5, MoF ₆ , MoCl ₆ , MoO ₃ , Mo(CO) ₆ , Na ₂ MoO ₄ ·2H ₂ O and (NH ₄ )6Mo ₇ O ₂₄ ·4H ₂ O It may be one or more selected from the group consisting of, preferably MoCl _5, Mo(CO) ₆ or a mixture thereof, and most preferably MoCl ₅ may be.

The precursor containing sulfur and nitrogen reacts with the molybdenum precursor _{to synthesize molybdenum disulfide (MoS 2} ) and at the same time doping nitrogen into the molybdenum disulfide structure to synthesize nitrogen-doped molybdenum sulfide in a simple way. The precursor including sulfur and nitrogen may be at least one selected from the group consisting of specifically thioacetamide, thiourea, and aminothiophenol. Preferably, it may be thioacetamide, thiourea, or a mixture thereof, and most preferably, it may be thioacetamide.

Using an acid generated in the process of synthesizing the nitrogen-doped molybdenum sulfide, the polymer precursor covers all or at least a part of the surface of the nitrogen-doped molybdenum sulfide to form a nitrogen-doped molybdenum sulfide/polymer complex. can be mixed. Specifically, the polymer precursor may be at least one selected from the group consisting of furfural, aniline, acetylene, pyrrole, and thiophene. Preferably, it may be furfural, aniline, or a mixture thereof, and most preferably, it may be furfural.

The solvent may be at least one selected from the group consisting of ethanol, propanol, methanol, butanol, pentanol, hexanol, acenonitrile, ethyl acetate, diethyl ether, trichloroethylene and diglomethane. Preferably, it may be at least one selected from the group consisting of ethanol, propanol, and methanol, and most preferably, ethanol.

In the step of preparing the mixture, the molybdenum precursor, the precursor containing sulfur and nitrogen, and the polymer precursor are 2.2: 7.7: 0.1 to 0.8: 7.7: 1.5 molar ratio, preferably 2.1: 7.7: 0.2 to 1: 7.7: 1.3 molar ratio, More preferably, it may be mixed in a molar ratio of 2: 7.7: 0.3 to 1.3: 7.7: 1, and most preferably in a molar ratio of 1.9: 7.7: 0.4. At this time, if the ratio of the polymer precursor is less than 0.1 mol, the content of the polymer is too small, so it is difficult to form a composite having a core-shell structure, and it may not be possible to control the particle size of the composite. Conversely, if the ratio of the polymer precursor exceeds 1.5 mol, the content of the polymer is too high, and thus, when the nitrogen-doped molybdenum sulfide/carbon composite is applied as an anode material, the movement of sodium ions may be hindered, thereby reducing charge/discharge performance.

In the step of preparing the nitrogen-doped molybdenum sulfide/polymer composite, molybdenum disulfide (MoS ₂ ) is synthesized by mixing the molybdenum precursor with a precursor containing sulfur and nitrogen, and at the same time, nitrogen is doped into the molybdenum disulfide structure. Nitrogen-doped molybdenum sulfide can be synthesized. In addition, the nitrogen-doped molybdenum sulfide/polymer complex can be mixed by using an acid generated in the process of synthesizing the nitrogen-doped molybdenum sulfide to cover all or at least a part of the surface of the nitrogen-doped molybdenum sulfide with a polymer precursor.

The step of preparing the nitrogen-doped molybdenum sulfide/polymer composite is performed by heating the mixture at 60-90° C. for 14-32 hours, preferably at 70-80° C. for 20-28 hours, more preferably at 73-78° C. 22 The reaction can be carried out for ˜26 hours, most preferably at 70° C. for 24 hours. At this time, if the reaction temperature and reaction time conditions are exceeded, nitrogen-doped molybdenum may not be properly formed, and the polymer precursor may be denatured by heat, so that the surface of the nitrogen-doped molybdenum may not be coated with a polymer.

In the step of preparing the nitrogen-doped molybdenum sulfide/carbon composite, the nitrogen-doped molybdenum sulfide is crystallized (crystallization) by heat treatment of the nitrogen-doped molybdenum sulfide/polymer composite, and a polymer covering the surface of the nitrogen-doped molybdenum sulfide. can be carbonized to porous carbon to prepare a final nitrogen-doped molybdenum sulfide/carbon composite. In this case, the heat treatment may be performed at 700 to 1000° C. for 30 minutes to 4 hours in a reducing atmosphere. Preferably it can be carried out at 750 to 890 °C for 1 to 3 hours, more preferably at 780 to 850 °C for 1.5 to 2.5 hours, and most preferably at 800 °C for 2 hours. At this time, if the heat treatment temperature is less than 700 ° C. or the time is less than 30 minutes, the polymer in the nitrogen-doped molybdenum sulfide / polymer composite is not carbonized properly, and charging and discharging performance may be reduced when applied as an anode material. Conversely, if the heat treatment temperature is greater than 1000° C. or the time is greater than 4 hours, the nitrogen-doped molybdenum sulfide/polymer composite may be deteriorated at a high temperature.

The reducing atmosphere may be performed in one or more inert gases selected from the group consisting of hydrogen gas, argon gas, helium gas, and nitrogen gas. Preferably, hydrogen gas or argon gas may be used, and most preferably hydrogen gas may be used.

The nitrogen-doped molybdenum sulfide/carbon composite may include a core including a nitrogen-doped molybdenum sulfide compound; and a shell portion including carbonized porous carbon, wherein the core portion may have a core-shell structure in which all or at least a portion of the surface of the core portion is covered by the shell portion.

The carbonized porous carbon may serve to control the particle size of the nitrogen-doped molybdenum sulfide/carbon composite, and when the composite is used as an anode material, the volume of the anode active material during charging and discharging is inhibited from expanding, resulting in structural stability can be improved, and it is possible to prevent the formation of a solid electrolyte interface (SEI) layer on the surface of the anode. In addition, it is possible to increase the life of the battery by suppressing the side reaction with the electrolyte.

The nitrogen-doped molybdenum sulfide/carbon composite may have an average particle size of 400 to 800 nm, preferably 450 to 750 nm, more preferably 480 to 700 nm, and most preferably 500 to 600 nm. At this time, if the average particle size is less than 400 nm, when the nitrogen-doped molybdenum sulfide/carbon composite is applied as a negative electrode material, the specific surface area of the negative electrode material becomes too large, and capacity loss due to irreversible reaction of sodium ions may occur, and vice versa If the average particle size is more than 800 nm, it is difficult to fabricate the electrode and may not be rolled properly.

The nitrogen-doped molybdenum sulfide/carbon composite is 0.1 to 10% by weight of carbon, preferably 0.5 to 8% by weight, more preferably 1 to 5% by weight, most preferably based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite For example, it may contain 3.04% by weight. At this time, if the carbon content is less than 0.1% by weight, it may be difficult to control the particle size of the nitrogen-doped molybdenum sulfide/carbon composite, and when this is applied as a negative electrode material, the volume expansion of the negative electrode active material during charging and discharging of the battery is suppressed may not be able to Conversely, when the carbon content is more than 10% by weight, when the nitrogen-doped molybdenum sulfide/carbon composite is applied as an anode material, the movement of sodium ions may be hindered, thereby reducing charge/discharge performance.

The nitrogen-doped molybdenum sulfide/carbon composite has a specific surface area (BET) of 3 to 20 m ² /g, preferably 5 to 15 m ² /g, more preferably 7 to 13 m ² /g, even more preferably it may be 8.5 ~ 12 m ² / g, most preferably 10.22 m ² / g. In addition, the nitrogen-doped molybdenum sulfide/carbon composite has an average pore size of 10-40 nm, preferably 18-35 nm, more preferably 20-32 nm, even more preferably 26-30 nm, most preferably may be 28.4 nm. At this time, if the specific surface area is ^{less than 3 m 2} /g or the average pore size is less than 10 nm, when the nitrogen-doped molybdenum sulfide/carbon composite is applied as an anode material, the passage of sodium ions is blocked and charging and discharging are repeated. The battery may deteriorate when Conversely, if the specific surface area is more ^{than 20 m 2} /g or the average pore size is more than 40 nm, when the nitrogen-doped molybdenum sulfide/carbon composite is applied as a negative electrode material, the electrolyte and sodium ions are formed on the surface of the negative electrode material during charging and discharging. An irreversible reaction may result in the consumption of sodium ions. As a result, the initial charge/discharge efficiency of the battery may decrease.

Preferably, in the method for preparing the nitrogen-doped molybdenum sulfide/carbon composite, in the step of preparing the mixture, the molybdenum precursor, the precursor containing sulfur and nitrogen, and the polymer precursor are 2.1: 7.7: 0.2 to 1: 7.7: 1.3 in a molar ratio. In the step of preparing the nitrogen-doped molybdenum sulfide/carbon composite, the heat treatment is performed at 750 to 890° C. for 1 to 3 hours under a reducing atmosphere, and the nitrogen-doped molybdenum sulfide/carbon composite has an average particle size of 480 ~700 nm, the nitrogen-doped molybdenum sulfide/carbon composite contains 0.5 to 8% by weight of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite, and the nitrogen-doped molybdenum sulfide/carbon composite has a specific surface area ( BET) may be 7-13 m ² /g, and the average pore size may be 20-32 nm.

When the molar ratio of the mixture and the heat treatment conditions, the carbon content of the nitrogen-doped molybdenum sulfide/carbon composite, the average particle size, the average pore size and the specific surface area are all satisfied, the nitrogen-doped molybdenum sulfide/carbon composite is crystallized by increasing the It is possible to prevent particle aggregation or coarsening, and to form uniform and even particles. As a result, it is possible to improve the physical and chemical stability of the battery and simultaneously increase the battery capacity, lifespan characteristics, and battery stability. If any one of the above conditions is not satisfied, the particles of the nitrogen-doped molybdenum sulfide/carbon composite are agglomerated or coarsened, so that the effect of simultaneously improving the capacity, lifespan, and battery stability of the battery cannot be expected at all. In addition, as the number of charge/discharge increases, the passage of sodium ions according to the nitrogen-doped molybdenum sulfide/carbon composite is blocked and the battery deteriorates.

More preferably, in the method for preparing the nitrogen-doped molybdenum sulfide/carbon composite, in the step of preparing the mixture, the molybdenum precursor, the precursor containing sulfur and nitrogen, and the polymer precursor are 2: 7.7: 0.3 to 1.3: 7.7: 1 molar ratio is mixed with, the molybdenum precursor is MoCl ₅ , the precursor containing sulfur and nitrogen is thioacetamide, the polymer precursor is furfural, and the heat treatment in the step of preparing the nitrogen-doped molybdenum sulfide / carbon composite is Carried out for 1.5 to 2.5 hours at 780 to 850 ° C. under a reducing atmosphere, the nitrogen doped molybdenum sulfide / carbon composite has an average particle size of 500 to 600 nm, and the nitrogen doped molybdenum sulfide / carbon composite is nitrogen doped molybdenum Containing 1 to 5% by weight of carbon based on the total weight of the sulfide/carbon composite, the nitrogen-doped molybdenum sulfide/carbon composite has a specific surface area (BET) of 8.5 to 12 m ² /g, and an average pore size of 26 to 30 It may be nm.

When all the optimized ranges of the molar ratio of the mixture, each precursor component, heat treatment conditions, carbon content of the nitrogen-doped molybdenum sulfide/carbon composite, average particle size, average pore size and specific surface area are satisfied, the nitrogen-doped molybdenum sulfide / When the carbon composite is applied as a negative electrode material, the overall reversibility of the negative electrode active material can be improved, and thermal stability and durability at low and high temperatures can be improved when charging and discharging are repeated.

On the other hand, the present invention is a core comprising a nitrogen-doped molybdenum sulfide compound; and a shell portion comprising carbonized porous carbon, wherein the core portion has a core-shell structure in which all or at least a portion of the surface is covered by the shell portion. /Provides a carbon complex. Preferably, the nitrogen-doped molybdenum sulfide/carbon composite may have a core-shell structure in which the entire surface of the core part is covered by the shell part.

The nitrogen-doped molybdenum sulfide/carbon composite may have an average particle size of 400 to 800 nm, preferably 450 to 750 nm, more preferably 480 to 700 nm, and most preferably 500 to 600 nm.

The nitrogen-doped molybdenum sulfide/carbon composite has a specific surface area (BET) of 3 to 20 m ² /g, preferably 5 to 15 m ² /g, more preferably 7 to 13 m ² /g, even more preferably it may be 8.5 ~ 12 m ² / g, most preferably 10.22 m ² / g. In addition, the nitrogen-doped molybdenum sulfide/carbon composite has an average pore size of 10-40 nm, preferably 18-35 nm, more preferably 20-32 nm, even more preferably 26-30 nm, most preferably may be 28.4 nm.

The nitrogen-doped molybdenum sulfide/carbon composite is 0.1 to 10% by weight of carbon, preferably 0.5 to 8% by weight, more preferably 1 to 5% by weight, most preferably based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite For example, it may contain 3.04% by weight.

In addition, the present invention provides an anode material for a sodium ion battery comprising the nitrogen-doped molybdenum sulfide/carbon composite.

In addition, the present invention provides a sodium ion battery comprising the negative electrode material.

As described above, the present invention uses a polymer obtained from a polymer precursor through an acid catalytic reaction as a shell portion to coat the surface of nitrogen-doped molybdenum sulfide, which is a core portion, and heat-treating it to crystallize nitrogen-doped molybdenum sulfide, and simultaneously carbonize the polymer. A nitrogen-doped molybdenum sulfide/carbon composite having a uniform particle size can be prepared.

In the nitrogen-doped molybdenum sulfide/carbon composite for sodium ion battery prepared in this way, the carbonized porous carbon, which is the shell part, controls the particle size of the composite. And it is possible to prevent the growth of the interfacial layer of the solid electrolyte on the surface of the negative electrode, it is possible to suppress the occurrence of the electrolyte side reaction to increase the life of the battery. In addition, the composite has a simple manufacturing process, and by improving the stability of the core-shell structure, electrochemical properties such as charge/discharge capacity, lifespan and rate of the sodium ion battery can be improved.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by the following examples.

Example 1: N-MoS ₂ /C complex manufacturing

Molybdenum chloride (MoCl ₅ ), Thioacetamide (CH ₃ CSNH ₂ ), Furfural (C ₅ H ₄ O ₂ ), and ethanol 99.9% (C ₂ H ₅ OH) were used as starting materials for the preparation of N-MoS _{2 /C complex.} did. First, 5 mmol (1.37 g) of molybdenum chloride and 20 mmol (1.50 g) of excess Thioacetamide were dissolved in 50 ml of ethanol. Then, 1 mmol (0.1 g) of Furfural was added to the solution and stirred. After stirring at room temperature for 30 minutes, the mixed solution was reacted at 70 °C for 24 hours, and the amorphous N-MoS ₂ /polymer complex was recovered through centrifugation. The recovered amorphous N-MoS ₂ /polymer complex was washed with distilled water and ethanol, and then dried in an oven at 80 °C for 10 hours. Then, the dried amorphous N-MoS ₂ / polymer composite is heat treated at 800 ° C. for 2 hours in a reducing atmosphere of Ar gas _{to carbonize the polymer in the N-MoS 2} / polymer composite to obtain the final N-MoS ₂ /C composite powder. got it

Comparative Example 1: MoS ₂ Ready

For comparison, commercial MoS ₂ powder purchased from Sigma-aldrich was prepared.

Comparative Example 2: N-MoS ₂ Produce

Molybdenum chloride (MoCl ₅ ), Thioacetamide (CH ₃ CSNH ₂ ), 99.9% ethanol (C ₂ H ₅ OH) were used as starting materials. First, 5 mmol (1.37 g) of molybdenum chloride and 20 mmol (1.50 g) of excess Thioacetamide were dissolved in ethanol (50 ml). Then, after stirring at room temperature for 30 minutes, the mixed solution was reacted at 70 ° C. for 24 hours, and then the amorphous N-MoS ₂ precipitate was recovered through centrifugation. The recovered amorphous N-MoS ₂ precipitate was washed with distilled water and ethanol and dried in an oven at 80 °C for 10 hours. _{Then, the final N-MoS 2} powder was obtained through a crystallization process of heat treatment at 800° C. for 2 hours in a reducing atmosphere of Ar gas.

Experimental Example 1: Scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) analysis

FE-SEM and TEM analysis were performed to confirm the shape and internal microstructure _{of the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2, and the results is shown in FIG. 2 .

2 is a scanning electron microscope (FE-SEM _{) of the MoS 2} , N-MoS ₂ and N-MoS ₂ /C composites prepared in Comparative Example 1 (a), Comparative Example 2 (b) and Example 1 (c). ) and transmission electron microscopy (TEM) analysis results are shown. In the case of (a) of FIG. 2 , _{it was confirmed that MoS 2} of Comparative Example 1 had particles having a sheet shape with a size of 1 μm or more. In addition, (b) the N-MoS of the Comparative Example 2 ₂ has a non-uniform particle size distribution, between the nano-particles (nanoparticles) aggregation phenomenon (agglomeration) is caused by the size of 500 ~ 600 nm N-MoS ₂ stumps observed.

In contrast, in (c), it was confirmed that the N-MoS ₂ /C composite of Example 1 formed a spherical powder having a uniform particle size distribution of 500 to 600 nm. Compared with the result of (b), it was found that furfural served as a carbon precursor and at the same time played a role in controlling the shape of the _{N-MoS 2 /C complex.}

Experimental Example 2: X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis

XRD analysis and XPS analysis were performed to confirm the crystal structure and surface composition _{of the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2, and the results are shown in FIG. 3 is shown.

3 is an X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis results of _{the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2; This is the graph shown. 3A shows the XRD patterns of Example 1 and Comparative Examples 1 and 2, and the position of each peak coincided with _{the MoS 2 structure corresponding to JCPDS card #37-1492.} It can be seen that sintering to form a hexagonal 2H-MoS ₂ structure without impurities is well completed, and it can be seen that the reaction is well performed without impurities or unreacted substances.

And (b) is described in Example 1 and Comparative Example 1, shows an XPS results of Figure 2, unlike MoS ₂ of the comparative example 1 of the Comparative Example 2 of the N-MoS ₂ in the Example 1 N-MoS ₂ The /C complex identified a peak at 396.6 eV for N1s. This is a peak for the formation of bonding linkages of Mo-N, and the N-MoS ₂ of Comparative Example 2 and the N-MoS ₂ /C composite of Example 1 obtained through the acid catalyst synthesis method are well doped with nitrogen bonding with Mo. was found to be In addition, when comparing the C1s peak, in Example 1 (N-MoS _{2 /C complex), unlike Comparative Example 1 (MoS 2} ) and Comparative Example 2 (N-MoS ₂ ), the three peaks located at 284.4, 285.9 and 287.0 eV The peaks can be separated, which correspond to the CC, CN and CO bonds, respectively. Through this, it was confirmed that the nitrogen-doped molybdenum sulfide/carbon composite was well synthesized through the acid catalyst synthesis method and the heat treatment process for crystallization and carbonization.

Experimental Example 3: BET (Brunauer Emmett Teller) analysis result

A nitrogen adsorption experiment was performed to confirm the specific surface area of _{the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2. Specifically, in the nitrogen adsorption experiment, nitrogen was adsorbed and desorbed to each material, and the surface area (BET) of the materials was calculated through the difference in the amount of adsorbed and desorbed nitrogen. The results are shown in FIG. 4 .

4 is a graph showing the surface area (BET) analysis results of _{the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2; Referring to FIG. 4 , the BET specific surface area as a result of the nitrogen adsorption experiment was _{1.91 m in Comparative Example 1 (MoS 2} ), Comparative Example 2 (N-MoS ₂ ) and Example 1 (N-MoS ₂ /C composite), respectively. ² /g, 2.46m ² /g and 10.22 m ² /g. In addition, unlike Comparative Examples 1 (MoS ₂ ) and 2 (N-MoS ₂ ), Example 1 (N-MoS ₂ /C composite) was found to have pores of 28.4 nm. That is, through the manufacturing process of Example 1 (N-MoS ₂ /C composite), it was confirmed that _{an N-MoS 2} /C composite having a carbon shell having a relatively large specific surface area and pores can be synthesized.

Experimental Example 4: Thermogravimetric analysis (TGA)

_{The N-MoS 2} /C composite prepared in Example 1 and Comparative Examples 1 and 2 _{, MoS 2} and N-MoS ₂ TGA analysis was performed to confirm the content of carbon contained in the composite, and the results are shown in FIG. indicated.

5 is a graph showing the thermogravimetric analysis (TGA) results of _{the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2; 5, the Example 1 (N-MoS ₂ /C composite) and Comparative Example 2 (N-MoS ₂ ) and Comparative Example 1 (MoS ₂ ) between 300 ~ 400 ℃ The material has a weight reduction of 10.54, 7.49, and 7.50 wt% of the total, respectively, and the _{reason for the greater weight reduction in Example 1 (N-MoS 2} /C composite) is the high carbon content and oxidation reaction of molybdenum sulfide. I could tell it was due. Through this, it was confirmed that the carbon content of Example 1 (N-MoS ₂ /C composite) was 3.04 wt%.

Experimental Example 5: Charge/discharge evaluation

_{In order to evaluate the electrochemical performance of the N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2, sodium half-cells were assembled with sodium metal as counter and reference electrodes. Charge/discharge was performed at room temperature (25°C) under current conditions of 0.1 C-rate. The results are shown in FIG. 6 .

6 is a graph showing the results of one-time charge/discharge evaluation of the sodium secondary battery prepared using the _{N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2; am. Referring to FIG. 6 , in the case of the first cycle at 0.1 C-rate (1 C-rate = 670 mA g ^-1 ), as shown in FIG. 5 , Comparative Example 1 (MoS ₂ ) and Comparative Example 2 (N-MoS ₂ ) had initial charge/discharge capacities of 393.02/468.95 mAh/g and 518.44/592.76 mAh/g, respectively, and Coulombic efficiency (CE) of 83.8% and 87.5%, respectively.

In contrast, the charge/discharge capacity of Example 1 (N-MoS ₂ /C composite) was 649.16/744.81 mAh/g, and CE was 87.2%, so that Example 1 (N-MoS ₂ /C composite) was The comparative example 1 (MoS ₂ ) showed superior reversible capacity and Na ⁺ ion charge/discharge efficiency. It was found that this phenomenon occurred because _{the MoS 2} composite of Comparative Example 1 having low electrical conductivity had limited diffusion of Na ^{+ in the electrochemical process.} In addition, it can be seen that the N-MoS ₂ /C composite of Example 1 is because the diffusion ^{of Na +} is made more easily during the charging and discharging process through the carbon shell having a large specific surface area and pores and having conductivity surrounding the N-MoS 2 /C composite. .

Experimental Example 6: Charge/discharge cycle evaluation

_{Example 1 (N-MoS 2} /C composite) at 0.2 C-rate using the same sodium half-cell as in Experimental Example 5 and Comparative Example 1 (MoS ₂ ) and Comparative Example 2 (N-MoS ₂ ) without carbon The lifespan characteristics after repeating the charge/discharge 200 times are shown in FIG. 7 .

_{7 is an N-MoS 2} /C composite prepared in Example 1 and Comparative Examples 1 and 2 _{, MoS 2} and N-MoS ₂ Charging capacity evaluation according to the number of charge/discharge cycles of the sodium secondary battery prepared using N-MoS 2 This is a graph showing the results. Referring to FIG. 7 , initially, CE of Example 1 and Comparative Examples 1 and 2 was relatively low. However, in the case of Example 1 (N-MoS ₂ /C composite), after 3 charge/discharge at 0.1 C-rate, CE was recovered to 95% or more at 0.2 C-rate, and 400.71 mAh / after 200 cycles A charge capacity of g was maintained.

In contrast, Comparative Example 2 (N-MoS ₂ ) and Comparative Example 1 (MoS ₂ ) have a serious capacity in which a low charge capacity of 212.85 mAh/g and 108.01 mAh/g is maintained after 200 cycles at 0.2C cycling, respectively. showed a decrease. This is the non-reversible phase generated by the conversion reaction with Na ⁺ of Comparative Example 1 (MoS ₂ ) and particle aggregation or coarsening due to the volume change of the material generated by repeating charge/discharge. (Coarsening) was found to be caused. In addition, in Example 1 (N-MoS ₂ /C composite), due to the carbon shell having a relatively large specific surface area and pores, the ^{de-/insertion process of Na +} is easier than that of Comparative Example 2 (N-MoS _{2 ).} could It was confirmed that the improved performance of Example 1 (N-MoS ₂ /C composite) was due to the presence of a conductive carbon shell as an electron path and a buffering role of the carbon composite structure for volume change in cycling.

Experimental Example 7: Rate characteristic evaluation

Rate characteristics were evaluated for the same sodium half-cell as in Experimental Example 5. The rate characteristic evaluation experiment was performed 5 times each at 0.1, 0.2, 0.5, 1, 2, 5, and 10 C-rates to confirm that the rate characteristics of the material were improved by the well-formed carbon composite structure. The results are shown in FIG. 8 .

8 is a graph showing the evaluation results of the rate characteristics of the sodium secondary battery prepared using the _{N-MoS 2} /C composite, MoS ₂ and N-MoS ₂ prepared in Example 1 and Comparative Examples 1 and 2. _{Referring to FIG. 8, in Example 1 (N-MoS 2} /C composite) in the fifth cycle at each C-rate based on 0.1 C-rate, the charge capacity reduction change rates were 100, 97.4, and 92.2, respectively. , 90.1, 88, 82.5, and 72.9%.

In contrast, in Comparative Example 2 (N-MoS ₂ ) and Comparative Example 1 (MoS ₂ ) without carbon, the capacity reduction change rate at each C-rate was 100, 96, 92.4, 90.3, 86.9, 75.5, 46.7 % and 100, 94.1, 84.7, 78, 71, 59.6, and 44.5%, indicating a relatively rapid change in dose reduction. Through this, in Example 1 (N-MoS ₂ /C composite), although the reversible capacity is reduced at a high current density, the Na ⁺ charge/discharge process is reversibly maintained well, and the comparative example 1 (MoS ₂ ) is higher than It was found that much more reversible capacity was maintained at the current density. This is because the removal/insertion process of ^{Na +} is easily performed even at high current density due to the presence of a conductive carbon shell having a large specific surface area and pores uniformly surrounding Example 1 (N-MoS _{2 /C composite).} Confirmed.

Claims (20)

preparing a mixture by mixing a molybdenum precursor, a precursor containing sulfur and nitrogen, a polymer precursor, and a solvent;
preparing a nitrogen-doped molybdenum sulfide/polymer complex by reacting the mixture at 60 to 90° C. for 14 to 32 hours; and
preparing a nitrogen-doped molybdenum sulfide/carbon composite by heat-treating the nitrogen-doped molybdenum sulfide/polymer composite;
including,
In the step of preparing the mixture, the molybdenum precursor, the precursor and the polymer precursor containing sulfur and nitrogen are mixed in a molar ratio of 2.1: 7.7: 0.2 to 1: 7.7: 1.3,
In the step of preparing the nitrogen-doped molybdenum sulfide/carbon composite, the heat treatment is performed at 750 to 890° C. for 1 to 3 hours under a reducing atmosphere,
The nitrogen-doped molybdenum sulfide/carbon composite has an average particle size of 480-700 nm, a specific surface area (BET) of 7-13 m ² /g, and an average pore size of 20-32 nm,
The nitrogen-doped molybdenum sulfide/carbon composite contains 0.5 to 8 wt% of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite. manufacturing method.
According to claim 1,
The molybdenum precursor is MoCl _{5 ,} MoF ₆ , MoCl ₆ , MoO ₃ , Mo(CO) ₆ , Na ₂ MoO ₄ .2H ₂ O and (NH ₄ )6Mo ₇ O ₂₄ .4H ₂ O One selected from the group consisting of The above method for producing a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure.
According to claim 1,
The precursor containing sulfur and nitrogen is at least one selected from the group consisting of thioacetamide, thiourea, and aminothiophenol. A method for producing a nitrogen-doped molybdenum sulfide/carbon composite for a core-shell structure sodium ion battery.
According to claim 1,
The polymer precursor is at least one selected from the group consisting of furfural, aniline, acetylene, pyrrole and thiophene. A method of manufacturing a nitrogen-doped molybdenum sulfide/carbon composite for a core-shell structure sodium ion battery.
According to claim 1,
The solvent is at least one selected from the group consisting of ethanol, propanol, methanol, butanol, pentanol, hexanol, acenonitrile, ethyl acetate, diethyl ether, trichloroethylene and diglomethane. Core-shell structure A method for producing a nitrogen-doped molybdenum sulfide/carbon composite for sodium ion batteries.
delete delete According to claim 1,
The reducing atmosphere is performed in at least one inert gas selected from the group consisting of hydrogen gas, argon gas, helium gas and nitrogen gas.
According to claim 1,
The nitrogen-doped molybdenum sulfide/carbon composite may include a core including a nitrogen-doped molybdenum sulfide compound; and a shell portion comprising carbonized porous carbon;
The method of manufacturing a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery having a core-shell structure in which the core part has a core-shell structure in which all or at least part of the surface is covered by the shell part.
delete delete delete delete According to claim 1,
In the step of preparing the mixture, the molybdenum precursor, the precursor and the polymer precursor containing sulfur and nitrogen are mixed in a molar ratio of 2: 7.7: 0.3 to 1.3: 7.7: 1,
The molybdenum precursor is MoCl ₅ ,
The precursor comprising sulfur and nitrogen is thioacetamide,
The polymer precursor is furfural,
In the step of preparing the nitrogen-doped molybdenum sulfide / carbon composite, the heat treatment is performed at 780 to 850 ° C. under a reducing atmosphere for 1.5 to 2.5 hours,
The nitrogen-doped molybdenum sulfide / carbon composite has an average particle size of 500 to 600 nm,
The nitrogen-doped molybdenum sulfide/carbon composite includes 1 to 5 wt% of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite,
The nitrogen-doped molybdenum sulfide/carbon composite has a specific surface area (BET) of 8.5 to 12 m ² /g and an average pore size of 26 to 30 nm. Nitrogen-doped molybdenum sulfide/ A method for producing a carbon composite.
a core comprising a nitrogen-doped molybdenum sulfide compound; and
A nitrogen-doped molybdenum sulfide/carbon composite comprising; a shell portion comprising carbonized porous carbon,
The core part has a core-shell structure in which all or at least part of the surface is covered by the shell part,
The nitrogen-doped molybdenum sulfide/carbon complex is a molybdenum precursor, a precursor containing sulfur and nitrogen, and a polymer precursor in a molar ratio of 2.1: 7.7: 0.2 to 1: 7.7: 1.3 by reacting a mixture of nitrogen-doped molybdenum sulfide/polymer It is formed by heat treatment after manufacturing the composite,
The heat treatment was performed at 750 to 890 ° C for 1 to 3 hours under a reducing atmosphere,
The nitrogen-doped molybdenum sulfide/carbon composite has an average particle size of 480-700 nm, a specific surface area (BET) of 7-13 m ² /g, and an average pore size of 20-32 nm,
The nitrogen-doped molybdenum sulfide/carbon composite is a nitrogen-doped molybdenum sulfide/carbon composite for a sodium ion battery of a core-shell structure comprising 0.5 to 8% by weight of carbon based on the total weight of the nitrogen-doped molybdenum sulfide/carbon composite.
delete delete delete A negative electrode material for a sodium ion battery comprising the nitrogen-doped molybdenum sulfide/carbon composite of claim 15.
A sodium ion battery comprising the negative electrode material of claim 19.

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