Negative electrode material for promoting sodium ion battery to realize long circulation

Abstract

The invention discloses a negative electrode material for promoting a sodium ion battery to realize long circulation, and particularly relates to a MoSe (at) rGO negative electrode material. In the preparation process of the negative electrode material, a sulfur source, a selenium source and a molybdenum source are uniformly stirred to prepare a dianionic compound (MoSSe). The invention firstly provides a double-anion combined action, a high-dispersity metal nano compound is obtained through the proportion of a selenium source and a sulfur source, electron / ion transfer can be accelerated by doping S into a MoSe2 crystal structure, the element Se can enlarge the interlayer spacing of MoS2, and the performance of MoS2 is improved. The composite material has the advantages of multiple active sites, high ion diffusion rate, extremely small volume expansion, good stability and the like, and can be used as a new strategy for improving the electrochemical performance of a secondary ion battery negative electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a negative electrode material for promoting a long cycle of a sodium ion battery. Background Art

[0002] Currently, sodium-ion batteries (SIBs) are considered to be viable candidates to replace lithium-ion batteries due to their lower cost and toxicity than lithium-based materials. After a decade of research, the electrochemical performance of SIBs cathode materials is now close to theoretical values. However, the low energy density and power density of SIBs anodes currently limit the practical application of SIBs in electronics. Metal sulfides / selenides / phosphides and intermetallic compounds have been developed to improve the performance of SIBs anodes. In conversion reactions, two-dimensional metal sulfides / selenides exhibit high energy density and low diffusion energy barriers, especially molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2), which are considered to be potential materials for high-performance SIBs. However, complex reaction mechanisms, large volume distortion, strong Na-S bonds, low conductivity, and dissolution of polysulfides / polyselenides limit the development of MoS2 electrodes.

[0003] In order to overcome the sluggish kinetics of MoS2 and narrow the gap between its theoretical and practical performance, previous research has focused on advanced MoS2 structures, including specific morphologies of buffer spaces, conductive material composites, phase structure tailoring, and ion exchange modifications; generally speaking, MoS2 anode materials should have buffer spaces to accommodate sodium ions (Na + ) volume expansion after insertion, such as vertical MoS2 nanosheet arrays, petal-shaped MoS2 nanosheets and 3D MoS2 / reduced graphene oxide (rGO) nanovesicles; nanostructured active materials and moderate pore content are key structural design elements for high-performance SIBs anodes; in addition, the low conductivity of MoS2 can be improved by forming a composite material with carbon materials; typically, carbon materials such as carbon nanotubes, carbon nanofibers, carbon spheres and reduced graphene oxide provide a path for fast electrons and prevent the agglomeration of negative electrode active materials; however, the negative electrode materials currently popular in the market still have the problem of large differences between theoretical performance and actual performance, and are prone to collapse during the charge and discharge cycle, resulting in poor cycle stability, which limits the practical application of SIBs. Summary of the invention

[0004] In view of this, the present invention provides a negative electrode material for promoting a long cycle of a sodium ion battery, specifically a MoSSe@rGO negative electrode material; the MoSSe@rGO negative electrode material has high energy density and excellent cycle stability, and MoSSe@rGO improves its Na +The storage kinetics enable the MoSSe@rGO anode to achieve breakthroughs in the cycle stability and rate performance of organic and solid-state electrolytes, with good results both in high-temperature and low-temperature environments.

[0005] The technical solution of the present invention is as follows: A negative electrode material that promotes long cycle of sodium ion batteries, the process is: Solution A is obtained by reacting ammonium tetrathiomolybdate with N,N-dimethylformamide (DMF), with vigorous stirring during the reaction; Solution B, selenium powder and hydrazine hydrate were continuously mixed at 75°C until the color of the solution turned reddish brown; Solution C, graphene oxide was dispersed in N, N-dimethylformamide (DMF) by ultrasonic treatment and continued stirring; Slowly adding solution B and solution C into solution A, and vigorously stirring for 30-40 minutes to obtain a mixed solution; pouring the mixed solution into a polytetrafluoroethylene-lined autoclave, reacting at 200° C. for 24-36 hours, cooling to room temperature, washing with water, and drying to obtain graphene oxide-supported MoSSe powder; The product was annealed at 500 °C for 2-3 h under Ar atmosphere to obtain the product MoSSe@rGO.

[0006] Preferably, the molar volume (mmol / mL) ratio of the ammonium tetrathiomolybdate to N,N-dimethylformamide is 0.7-1.5:60.

[0007] Preferably, the concentration of hydrazine hydrate is 80%; the molar volume (mmol / mL) ratio of selenium powder to hydrazine hydrate is 1.5-2.5:10.

[0008] Preferably, the molar volume (mmol / mL) ratio of selenium powder to hydrazine hydrate is 2:10.

[0009] Preferably, the weight volume ratio (mg / mL) of graphene oxide to N,N-dimethylformamide is 45:55-60:40; Preferably, graphene oxide is dispersed in N,N-dimethylformamide (DMF) by ultrasonic treatment, ultrasonic dispersion is performed for 60 minutes, and stirring is continued for 60 minutes to obtain solution C.

[0010] Preferably, the black precipitate is washed with deionized water and anhydrous ethanol.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The product MoSSe@rGO obtained by the present invention is prepared by a simple one-pot hydrothermal method; In the present invention, graphene nanosheets provide a fast electron diffusion path and adapt to the volume expansion caused by sodium ion deintercalation during the charge and discharge process; by improving the electrochemical performance of MoSSe@rGO, the double anion (S 2− and Se 2− ) Synergistic effect of doping; Se 2− The introduction of increases the interlayer spacing of MoS2, forming a 2H / 1T hybrid phase, resulting in a wider ion channel and metallic properties; The MoSSe@rGO electrode obtained by the present invention has good cycle stability (0.5A g -1 After 300 cycles of charge and discharge at a current density of 1.5 %, the discharge capacity can still be maintained at 550 mAh g -1 ) and excellent rate performance (330mAh g -1 @10A -1 ), suitable for organic liquid batteries and inorganic solid-state batteries in a wide temperature range; even at a current density of 10 A g -1 In the case of 2.5 mAh g-1, the MoSSe@rGO electrode also maintains a high capacity of 338.5 mAh g-1 in liquid electrolyte. -1 This work provides a design strategy for anode materials suitable for SIBs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 The MoSSe@rGO in Example 1 at 0.5A g -1 Charge and discharge cycle performance under different current densities.

[0014] Figure 2 The MoSSe@rGO in Example 1 at 10.0A g -1 Charge and discharge cycle performance under different current densities.

[0015] Figure 3 This is the rate performance of MoSSe@rGO at different current densities in Example 1. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0017] As described in the research background, the kinetics of MoSe2 in the prior art are slow, there is a large gap between its theoretical and actual performance, and the material is prone to collapse during the battery cycle, which is not conducive to the cycle. Based on this, the present invention is the first to propose a negative electrode material that promotes the long cycle of sodium metal batteries. The present invention is further described below in conjunction with specific embodiments.

[0018] Ammonium tetrathiomolybdate, N,N-dimethylformamide (DMF), selenium powder, sulfur powder, and hydrazine hydrate were purchased from Sinopharm Chemical Reagent Co., Ltd. All chemicals were used directly without further purification. Deionized water (18 MΩ cm −1 ) were obtained through a Barnstead Nanopure water system (Aqua Solutions); graphene oxide was homemade in the laboratory using the Hummers method.

[0019] In the present invention, the stirring speed of the vigorous stirring is 1000 rpm / min.

[0020] Example 1 A negative electrode material for promoting a long cycle of a sodium ion battery, the preparation process of which is as follows: Step 1, solution A, dissolve 1 mmol of ammonium tetrathiomolybdate in 60 mL of N,N-dimethylformamide (DMF), and stir vigorously for 60 min to obtain solution A; Step 2, solution B, 2 mmol of selenium powder is dispersed in 10 mL of hydrazine hydrate, the concentration of hydrazine hydrate is 80%; then, the mixture is continuously mixed at 75° C. until the color of the solution turns reddish brown, to obtain solution B; Step 3, solution C, 50 mg of graphene oxide was dispersed into 50 mL of N, N-dimethylformamide (DMF) by ultrasonic treatment, and ultrasonic dispersion was performed for 60 min; then stirring was continued for 60 min to obtain solution C; Step 4: slowly add solution B and solution C into solution A, and stir vigorously for 30 min to obtain a mixed solution; The mixed solution was poured into a 100 mL polytetrafluoroethylene-lined autoclave, reacted at 200°C for 24 hours, cooled to room temperature, washed with water and dried to obtain graphene oxide-supported MoSSe powder; Step six, anneal the MoSSe powder at 500 °C for 2 h in an Ar atmosphere to obtain the product MoSSe@rGO.

[0021] The obtained product MoSSe@rGO was used as an active material to prepare the negative electrode material of sodium ion battery. The counter electrode used a sodium sheet prepared in the laboratory and the diaphragm used a Whatman glass fiber diaphragm. The electrolyte was NaPF6 in DME. The 2032 type button battery was assembled. The obtained button battery was placed on a Blue Electric electrochemical charge and discharge instrument for constant current charge and discharge. Figure 1 , 2 are respectively at 0.5 / 10A g -1 Charge and discharge cycle performance under different current densities. Figure 3 This is the rate performance of MoSSe@rGO at different current densities.

[0022] Example 2 In this embodiment, the selenium source is removed to obtain MoS2, and the specific steps are as follows: Step 1, solution A, dissolve 1 mmol of ammonium tetrathiomolybdate in 60 mL of N,N-dimethylformamide (DMF), and stir vigorously for 60 min to obtain solution A; Step 2, Solution B, 2 mmol of sulfur powder is dispersed in 10 mL of hydrazine hydrate, the concentration of hydrazine hydrate is 80%; then continuously mixed at 75°C until the color of the solution turns reddish brown, to obtain Solution B; Step 3, solution C, 50 mg of graphene oxide was dispersed into 50 mL of N, N-dimethylformamide (DMF) by ultrasonic treatment, and ultrasonic dispersion was performed for 60 min; then stirring was continued for 60 min to obtain solution C; Step 4: slowly add solution B and solution C into solution A, and stir vigorously for 30 min to obtain a mixed solution; The mixed solution was poured into a 100 mL polytetrafluoroethylene-lined autoclave, reacted at 200 °C for 24 hours, cooled to room temperature, washed with water and dried to obtain graphene oxide-supported MoS2 powder; Step six, annealing the MoS2 powder at 500°C for 2 hours in an Ar atmosphere to obtain the product MoS2@rGO.

[0023] Example 3 In this embodiment, the sulfur source is removed to obtain MoSe2, and the specific steps are as follows: Step 1, solution A, dissolve 1 mmol of ammonium tetraselenomolybdate in 60 mL of N,N-dimethylformamide (DMF), and stir vigorously for 60 min to obtain solution A; Step 2, solution B, 2 mmol of selenium powder is dispersed in 10 mL of hydrazine hydrate, the concentration of hydrazine hydrate is 80%; then, the mixture is continuously mixed at 75° C. until the color of the solution turns reddish brown, to obtain solution B; Step 3, solution C, 50 mg of graphene oxide was dispersed into 50 mL of N, N-dimethylformamide (DMF) by ultrasonic treatment, and ultrasonic dispersion was performed for 60 min; then stirring was continued for 60 min to obtain solution C; Step 4: slowly add solution B and solution C into solution A, and stir vigorously for 30 min to obtain a mixed solution; The mixed solution was poured into a 100 mL polytetrafluoroethylene-lined autoclave, reacted at 200°C for 24 hours, cooled to room temperature, washed with water and dried to obtain graphene oxide-supported MoSe2 powder; Step six, anneal the MoSe2 powder at 500°C for 2 hours in an Ar atmosphere to obtain the product MoSe2@rGO.

[0024] In the present invention, a sulfur source, a selenium source and a molybdenum source are uniformly stirred to prepare a double anion compound (MoSSe); the present invention first proposes a double anion synergy, and obtains a highly dispersed metal nanocompound by adjusting the ratio of the selenium source to the sulfur source. Doping S into the MoSe2 crystal structure can accelerate the transfer of electrons / ions, and the element Se can expand the interlayer spacing of MoS2. It has the advantages of many active sites, fast ion diffusion rate, extremely small volume expansion and good stability, and can be used as a new strategy to improve the electrochemical performance of negative electrode materials for secondary ion batteries.

[0025] Although the present invention has been described in detail by reference to the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A negative electrode material for promoting a long cycle of a sodium ion battery, characterized in that: The process is: Solution A is obtained by reacting ammonium tetrathiomolybdate with N,N-dimethylformamide, with vigorous stirring during the reaction; Solution B, selenium powder and hydrazine hydrate were continuously mixed at 75°C until the color of the solution turned reddish brown; Solution C, graphene oxide was dispersed in N,N-dimethylformamide by ultrasonic treatment and continued stirring; Slowly adding solution B and solution C into solution A, and vigorously stirring for 30-40 minutes to obtain a mixed solution; pouring the mixed solution into a polytetrafluoroethylene-lined autoclave, reacting at 200° C. for 24-36 hours, cooling to room temperature, washing with water, and drying to obtain graphene oxide-supported MoSSe powder; The product was annealed at 500 °C for 2-3 h under Ar atmosphere to obtain the product MoSSe@rGO.

2. The negative electrode material for promoting long cycle of sodium ion battery according to claim 1, characterized in that: The molar volume (mmol / mL) ratio of the ammonium tetrathiomolybdate to N,N-dimethylformamide is 0.7-1.5:

60.

3. The negative electrode material for promoting long cycle of sodium ion battery according to claim 1, characterized in that: The concentration of hydrazine hydrate is 80%; the molar volume (mmol / mL) ratio of selenium powder to hydrazine hydrate is 1.5-2.5:

10.

4. The negative electrode material for promoting long cycle of sodium ion battery according to claim 3, characterized in that: The molar volume (mmol / mL) ratio of selenium powder to hydrazine hydrate is 2:

10.

5. The negative electrode material for promoting long cycle of sodium ion battery according to claim 1, characterized in that: The weight volume (mg / mL) ratio of graphene oxide to N,N-dimethylformamide is 45:55-60:

40.

6. The negative electrode material for promoting long cycle of sodium ion battery according to claim 5, characterized in that: The graphene oxide was dispersed into N,N-dimethylformamide by ultrasonic treatment, ultrasonic dispersion was performed for 60 minutes, and stirring was continued for 60 minutes to obtain solution C.

7. The negative electrode material for promoting long cycle of sodium ion battery according to claim 1, characterized in that: The black precipitate was washed with deionized water and anhydrous ethanol.

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