Preparation method and normal / low temperature application of ferrous disulfide-graphene aerogel composite electrode material

Abstract

The invention relates to a preparation method and normal / low temperature application of a ferrous disulfide-graphene aerogel composite electrode material. The material comprises a three-dimensional porous graphene aerogel skeleton and ferrous disulfide nanoparticles loaded on three-dimensional porous graphene aerogel. The specific preparation method comprises the following steps: firstly, synthesizing nanoscale ferroferric oxide through hydrothermal reaction under the regulation and control of TEA (triethanolamine), then carrying out hydrothermal compounding on the nanoscale ferroferric oxide and graphene oxide, and freeze-drying to form a ferroferric oxide-graphene aerogel precursor; finally, the precursor is converted into the ferrous disulfide-graphene aerogel composite material through a solid-phase vulcanization method. The conductivity of the material is improved, the contact area of an electrode and an electrolyte is increased, active sites are increased, the problem of volume expansion of the material in the charging and discharging process is relieved, and the material shows good rate capability and cycling stability in normal-temperature and low-temperature environments as a sodium-ion battery negative electrode material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery materials, and in particular to a preparation method and application of a ferrous disulfide-graphene aerogel composite electrode material. BACKGROUND

[0002] Sodium-ion batteries (SIBs) have similar energy storage mechanisms to lithium-ion batteries (LIBs), and are widely considered as a substitute for LIBs due to their suitable potential, low cost, and other characteristics. In the past few decades, SIBs have made significant progress, especially in terms of cycle stability and high-rate performance. It can be predicted that, with the rapid expansion of demand for large-scale grid energy storage, aerospace, offshore exploration and national defense applications, the low-temperature performance of SIBs will face more severe challenges. Due to the small Stokes diameter of sodium ions and the high ionic conductivity, SIBs should have stronger application advantages in low-temperature environments. However, in actual operation, the problem of rapid performance degradation of batteries caused by low temperature is still difficult to avoid. A series of studies have shown that the reduction of diffusion rate in the bulk phase of the electrode material is one of the reasons for the poor performance of SIBs at extremely low temperatures. + The reduction of diffusion rate in the bulk phase of the electrode material is one of the reasons for the poor performance of SIBs at extremely low temperatures.

[0003] Among various anode materials, transition metals are considered the most promising candidates due to their high theoretical capacity, easily controllable structure, excellent reversible redox chemical performance and environmental friendliness. Among them, ferrous disulfide (FeS2) is considered to be a highly practical potential anode material due to its abundant reserves, environmental friendliness, low cost and high theoretical capacity of 894 mAh g -1 based on the conversion reaction FeS2+ 4Na → 2Na2S + Fe. In addition, as a typical conversion-type anode, FeS2 generates a large amount of Fe nanoparticles with superparamagnetic properties during the reaction process. The 3d orbital electrons of such Fe nanoparticles are not full, can form a space charge region and induce a spin-polarized surface capacitance effect. This effect not only can store additional Na + , but also can significantly enhance the diffusion dynamics of sodium ions at low temperatures. Therefore, FeS2 has sufficient potential to be used as an anode material for high-performance low-temperature sodium-ion batteries. However, the electronic conductivity of the FeS2 electrode is poor, and the volume change during cycling is huge (280%), which directly leads to poor rate performance and poor cycle stability of the battery when used as a negative electrode material for sodium-ion batteries. Therefore, it is crucial to find an anode material with long cycle life, high energy and power density and normal use at extremely low temperatures. SUMMARY

[0004] The application aims at the above problems, and provides a preparation method of a GA electrode material and normal / low temperature application. + The slow diffusion problem in the electrode body phase is solved; meanwhile, the presence of the three-dimensional graphene aerogel (GA) not only provides a buffer space for the volume expansion of the active particles, inhibits the agglomeration of the active substances, and constructs an efficient continuous electron conduction network, but also further improves the specific capacity and cycle stability of the electrode material. The electrode prepared by the application expands the room temperature and low temperature application of the carbon composite material in the sodium ion battery negative electrode material.

[0005] To achieve the above-mentioned application purposes, the application adopts the following technical solutions. a. 0.4~0.6 g of ferric chloride hexahydrate and 2~5 mL of TEA are weighed and dissolved in 20~50 mL of deionized water, and a Fe(III)-TEA uniform solution is formed under vigorous stirring at room temperature.

[0006] b. The mixed solution obtained in step a is transferred to an 80 mL high-pressure reaction kettle with a polytetrafluoroethylene lining, and is placed in an oven and heated to 160~200℃ for 1~3 h. The obtained nano-sized Fe3O4 is repeatedly washed with deionized water for several times and dried to obtain nano-sized Fe3O4.

[0007] c. The prepared graphene oxide (rGO) is prepared into a solution with a concentration of 2~2.5 mg mL -1 , 4~7 mL of the graphene oxide solution with the above concentration is taken and placed in a 15 mL glass bottle, and is ultrasonically treated for 80~100 min.

[0008] d. 10~50 mg of the nano-sized Fe3O4 prepared in step b is dissolved in the solution in step c, and a uniform mixed solution is obtained after stirring at room temperature for 2~5 h.

[0009] e. The solution obtained in step d is transferred to an 80 mL high-pressure reaction kettle with a polytetrafluoroethylene lining, and is placed in an oven and heated to 160~200℃ for 4~8 h.

[0010] f. After the hydrothermal treatment, the glass bottle is taken out after the reaction kettle is cooled to room temperature, and is repeatedly washed with deionized water for several times and freeze-dried for 36~48 h to obtain the Fe3O4@GA material.

[0011] g. The Fe3O4@GA material prepared in step f and sulfur powder are mixed uniformly at a mass ratio of 1:4 to 1:8 and then placed in a porcelain boat.

[0012] h. The porcelain boat in step g is placed in a quartz tube, annealed at 450-600°C at a rate of 1-5 ℃ / min under an argon atmosphere for 4-8 h to obtain a FeS2@GA material.

[0013] Compared with the prior art, the method has the following obvious substantial features and advantages: The synthesized FeS2 nanoparticles have a small size, effectively shortening the ion and electron transmission path, improving the migration rate, and relieving the low-temperature environment Na + diffusion in the bulk phase of the electrode material, thereby improving the rate performance and excellent low-temperature performance of the battery. Meanwhile, nanocrystallization increases the specific surface area of the material, providing more embedding / detaching reaction active sites for sodium ions and improving the reversible specific capacity. Meanwhile, the FeS2 and three-dimensional porous graphene aerogel (GA) are combined to form a composite material, which improves the conductivity of the material, relieves the volume expansion problem of FeS2 during the charging and discharging process, and strengthens the cycle stability, rate performance, and low-temperature specific capacity of the composite material when used as a negative electrode material for a sodium ion battery. The three-dimensional porous graphene aerogel composite material loaded with FeS2 nanoparticles prepared by the method has excellent rate performance as a sodium ion negative electrode material at room temperature and has a good battery capacity retention rate. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 SEM image of the FeS2 / graphene aerogel electrode material in the examples of the present application; Figure 2 XPS image of the FeS2 / graphene aerogel electrode material in the examples of the present application; Figure 3 Cycle performance graph of the FeS2 / graphene aerogel electrode material at room temperature in the examples of the present application; Figure 4 Rate performance graph of the FeS2 / graphene aerogel electrode material at room temperature in the examples of the present application; Figure 5 Cycle performance comparison graph of the FeS2 / graphene aerogel electrode material in the examples of the present application at room temperature and in a low-temperature environment. DETAILED DESCRIPTION

[0015] To fully elucidate the technical solution and practical effects of the present invention, the core concept, implementation process, and resulting technical benefits of the present invention will be systematically described below in conjunction with specific embodiments. These embodiments are intended to provide detailed evidence for understanding the purpose, innovative features, and technical advantages of the present invention; however, it should be understood that the scope of protection of the present invention is not limited to the listed embodiments. The above solution will be further described below with reference to specific embodiments, and preferred embodiments of the present invention are detailed below: All reagents used in this invention are commercially available products.

[0016] Example: A method for preparing a ferrous disulfide / three-dimensional porous graphene aerogel (GA) composite electrode material includes the following steps: Step a: Weigh 0.54 g of ferric chloride hexahydrate and 4 mL of TEA and dissolve them in 40 mL of deionized water. Stir vigorously at room temperature to form a homogeneous Fe(III)-TEA solution.

[0017] Step b: Transfer the mixed solution obtained in step a to an 80 mL high-pressure reactor lined with polytetrafluoroethylene, place it in an oven, heat to 180°C, and react for 1.5 h. Wash repeatedly with deionized water several times, and dry to obtain nano-sized 3O4.

[0018] Step c, prepare the graphene oxide to a concentration of 2 mg / mL. -1 Take 5 mL of the graphene oxide solution of this concentration and place it in a 15 mL glass bottle, then sonicate for 90 min.

[0019] Step d: Dissolve 30 mg of the nano-sized Fe3O4 prepared in step b in the solution in step c above, and stir at room temperature for 3 h to obtain a homogeneous mixed solution.

[0020] Step e: Transfer the solution obtained in step d above to an 80 mL high-pressure reactor with a polytetrafluoroethylene liner, place it in an oven, heat it to 190°C, and react for 6 h.

[0021] Step f: After hydrothermal treatment, once the reactor has cooled to room temperature, remove the glass bottle, wash it repeatedly with deionized water several times, and freeze-dry it for 36 h to obtain the 3O4@GA composite material.

[0022] Step g: Mix the Fe3O4@GA composite material and sulfur powder obtained in step f at a mass ratio of 1:5 and place them in a ceramic boat.

[0023] In step h, the ceramic boat from step g is placed in a quartz tube and annealed at 550 °C for 6 hours under an argon atmosphere at a rate of 2 °C / min. This yields the FeS2@GA composite material.

[0024] To verify the successful synthesis of a ferrous disulfide / three-dimensional porous graphene aerogel composite material in this invention, its morphology and composition were characterized. Figure 1 The image shows a scanning electron microscope (SEM) image of the 2@GA prepared in this invention example. The image shows that many graphene sheets are cross-linked to form a three-dimensional porous carbon network. On the graphene aerogel, small-sized ferrous disulfide particles are evenly distributed. Figure 2 The X-ray photoelectron (XPS) spectrum of the FeS2@GA composite electrode material prepared for this invention clearly shows the presence of Fe, S, C, and O elements, with the O 1s peak attributed to the sample's exposure to air. This demonstrates the successful synthesis of the FeS2@GA composite material.

[0025] Testing the performance of sodium-ion batteries: To verify the performance of the FeS2@GA composite electrode material of the present invention, the prepared FeS2@GA composite electrode material, polyvinylidene fluoride (PVDF), and conductive carbon black were mixed in a mass ratio of 8:1:1 and adjusted into a uniform slurry with 1-methyl-2-pyrrolidone (NMP). Copper foil was used as the current collector to prepare the FeS2@GA composite electrode sheet. A sodium metal sheet was used as the counter electrode, a GF / D type Whatman glass fiber filter membrane was used as the separator, and a 1M NaPF6 DIG solution was used as the electrolyte. The button cell assembly was then tested at room temperature and low temperature using an electrochemical workstation. 图3是本发明实施例制备得到的FeS2@GA的常温下循环性能图，结果显示在0.5 A g-1 At a current density of 623.6 mAh g⁻¹, after 100 charge-discharge cycles, its specific capacity was obtained. -1 It exhibits excellent cycle stability. Figure 4 This is a rate performance diagram of FeS2@GA prepared in the embodiments of the present invention at room temperature, at 0.1, 0.2, 0.5, 1, 2, 5 and 10 Ag. -1 At current density, FeS2@GA的可逆容量分别为671.1 646.8, 623.9, 606.9, 597.1, 543.7 and 480.1 mAh g -1 , -1 Under high current density FeS2@GA仍能保持360.3 mAh g-1 Reversible capacity, -1 At that time, the specific capacity recovered to 658.9 mAh g. -1 It exhibits good rate capability. Figure 5 This is a comparison of the cycling performance of FeS2@GA prepared in the embodiments of the present invention at room temperature and low temperature. At -40℃, as a sodium-ion battery anode material, at 0.5 A g... -1 At current density, it retains 56% of the specific capacity compared to the room temperature scenario.

Claims

1. A method for preparing a ferrous disulfide-graphene aerogel composite electrode material, characterized in that... It has the following process and steps: a. Dissolve ferric chloride hexahydrate and TEA in deionized water and stir vigorously at room temperature to obtain a homogeneous Fe(III)-TEA solution; b. Transfer the mixed solution obtained in step a above to a high-pressure reactor with a polytetrafluoroethylene liner and place it in an oven for reaction. Wash with deionized water and dry to obtain nano-sized iron(III) oxide (Fe3O4); c. Prepare a graphene oxide (rGO) solution and place it in a glass bottle for ultrasonication; d. Dissolve the nano-sized iron(III) oxide (Fe3O4) prepared in step b in the solution in step c above, stir, and obtain a homogeneous mixed solution; e. Transfer the solution obtained in step d above to a high-pressure reactor with a polytetrafluoroethylene liner and heat it in an oven; f. After hydrothermal treatment, once the reactor has cooled to room temperature, remove the glass bottle, wash it with deionized water, and freeze-dry it to obtain the Fe3O4@GA aerogel material. g. After forming a uniform mixture with sulfur powder, the Fe3O4@GA / Fe3O4 aerogel material prepared in step f above is placed in a ceramic boat; h. Place the ceramic boat from step g above into a quartz tube, and anneal it under an argon atmosphere after heating. This yields ferrous disulfide / graphene aerogel (FeS2@GA) material.

2. The preparation method according to claim 1, characterized in that, In step a, the amount of ferric chloride hexahydrate added is 0.4~0.6g, and the amount of TEA is 2~5mL. Ferric chloride hexahydrate and TEA are dissolved in 20~50mL of deionized water.

3. The preparation method according to claim 1, characterized in that, The reactor specifications in step b include one of 60mL, 80mL, and 100mL, the oven heating temperature is 160~200℃, and the heating time is 1~3 hours.

4. The preparation method according to claim 1, characterized in that, In step c, the concentration of the graphene oxide solution is prepared to be 2~2.5 mg / mL. -1 The range of graphene oxide solution used is 4-7 mL, and the sonication time is 80-100 min.

5. The preparation method according to claim 1, characterized in that, In step d, the amount of nano-sized iron oxide prepared in step b is 10-50 mg, and the stirring time is 2-5 h.

6. The preparation method according to claim 1, characterized in that, The reactor specifications in step e include one of 60mL, 80mL, and 100mL, and the oven heating temperature is 160~200℃, with a heating time of 4~8 h.

7. The preparation method according to claim 1, characterized in that, The freeze-drying time in step f is 36~48 h.

8. The preparation method according to claim 1, characterized in that, In step g, the mass ratio of iron oxide / graphene aerogel material to sulfur powder in the mixture is 1:(4~8).

9. The preparation method according to claim 1, characterized in that, In step h, the heating rate is 1~5 ℃ / min, the heating temperature is 450~600℃, and the annealing time is 4~8 h.

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