Preparation method and application of polymetallic sulfide-expanded graphite composite material

Abstract

The invention belongs to the technical field of micro-nano composite materials, and particularly relates to a preparation method and application of a multi-metal sulfide-expanded graphite composite material. The preparation method of the multi-metal sulfide-expanded graphite composite material comprises the following steps: recovering graphite negative electrodes of waste lithium ion batteries, constructing cross-linked porous three-dimensional expanded graphite through a controllable expansion strategy, uniformly loading multi-metal sulfide nanoparticles on the surface of the expanded graphite by adopting a hydrothermal method, and carrying out heat treatment to obtain the composite material. The three-dimensional grid structure of the expanded graphite not only provides uniformly dispersed anchoring points for the polymetallic sulfide nanoparticles, but also constructs a continuous conductive network. According to the heterogeneous interface engineering, the charge transfer resistance is reduced, and agglomeration and volume expansion of active substances in circulation are inhibited through the topological confinement effect. The polymetallic sulfide-expanded graphite composite material prepared by the method has good structural stability and electrical conductivity, and the cycling stability of a battery can be remarkably improved when the polymetallic sulfide-expanded graphite composite material is used as a battery material.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a multi-metal sulfide-expanded graphite composite material, which can be used as an electrode material for lithium / sodium ion batteries and belongs to the field of new energy materials. Background Art

[0002] With the continuous growth of global energy demand and the increasing awareness of environmental protection, lithium-ion batteries, as an efficient and clean energy storage device, have been widely used in many fields, from portable electronic devices to large power systems such as electric vehicles, and their market scale has shown a rapid expansion trend. Therefore, it is crucial to develop environmentally friendly materials with good lithium storage performance. In the research field of lithium-ion batteries, the performance optimization of anode materials has always been one of the key research directions. Transition metal sulfides are recognized as promising next-generation high-energy density anode materials due to their high theoretical specific capacity (800 mAh·g -1 ), controllable nanostructure tunability, and multi-electron redox characteristics. However, their intrinsic low electrical conductivity (<10 -3 S·cm -1 ), severe volume deformation (>200%), and sluggish ion diffusion kinetics severely restrict their practical applications.

[0003] To further overcome these drawbacks, researchers have made great efforts in material and structure design. First, by nanosizing the material, the stress generated by volume expansion can be effectively released. At the same time, with the expansion of the contact area between the electrode and the electrolyte, the migration of lithium ions may become easier. Second, constructing a heterostructure can not only promote the formation of an internal electric field but also enhance the activity of the electrochemical reaction at the heterointerface, thereby improving the electrical conductivity. In addition, the heterointerface contains more defects, which provide sufficient active sites for the insertion and extraction of ions. Finally, by hybridizing bimetal sulfides with various carbon-containing materials such as graphene or carbon nanotubes, the electrical conductivity of the composite material can be significantly improved, and the continuous carbon network can also significantly alleviate the volume expansion effect during charge and discharge. Although remarkable achievements have been made, due to the limited improvement in electrical conductivity, structure, and electrochemical stability by single modification methods, it still seems not to reach the level of practical application. Combining the above three strategies will endow the electrode with high electrical conductivity, fast charge transfer ability, and good interfacial behavior at the same time. The key to implementing the above strategies is to find a suitable matrix for loading metal sulfides.

[0004] Expanded graphite has a unique structure and excellent properties, and is regarded as an ideal candidate material for energy storage. Expanded graphite has a rich pore structure and a large specific surface area, which provide an ideal site for the uniform dispersion of bimetallic sulfides, can effectively prevent the aggregation of nanoparticles, thereby increasing the number of active sites and improving the overall utilization rate of the material. At the same time, expanded graphite itself has good electrical conductivity and can serve as a high-speed channel for electron transport, thus improving the conductivity problem of bimetallic sulfides and promoting the kinetic process of electrode reactions. In addition, the flexibility and mechanical stability of expanded graphite help to buffer the volume expansion of bimetallic sulfides during charge and discharge, maintain the stability of the electrode structure, reduce the loss of active substances, and further improve the cycling performance of the battery. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of a multi-metal sulfide-expanded graphite composite material, using cross-linked porous three-dimensional expanded graphite derived from waste graphite as a conductive matrix, by compounding with high-capacity bimetallic sulfides, using the high electrical conductivity of expanded graphite to shorten the lithium ion diffusion path, inhibit volume expansion, and leveraging the synergistic effect of the composite material to improve the electrode conductivity and sulfide stability, ultimately achieving an effective combination of structural optimization and resource utilization of waste batteries.

[0006] The present invention is specifically realized through the following technical solutions. A preparation method of a waste graphite-derived expanded graphite-based bimetallic sulfide nanocomposite material according to the present invention is characterized in that the specific process is as follows:

[0007] Step S1. Disassemble the discarded ternary battery to remove the negative electrode sheet, and collect the materials on the negative electrode sheet by ultrasonic washing.

[0008] Step S2. Configure a mixed acid solution in a reaction kettle, transfer the waste graphite material into the mixed acid solution, and slowly add potassium permanganate thereto under stirring, and continue stirring for a certain time.

[0009] Step S3. Filter and wash the mixed solution to obtain graphite oxide. Place the graphite oxide in a tubular furnace, set the calcination temperature and calcination time under the protection of an inert atmosphere, and naturally cool to room temperature to obtain expanded graphite.

[0010] Step S4. Disperse the expanded graphite in an organic solvent by ultrasonic dispersion.

[0011] Step S5. Add a certain amount of metal salt to the solution in Step S4, and stir at room temperature for a certain time.

[0012] Step S6. Weigh a certain amount of thiourea compound and add it to the mixed solution in Step S5, and magnetically stir for a certain time at room temperature. Transfer the mixed solution to a stainless-steel reactor with a polytetrafluoroethylene lining, and transfer the reactor to an oven. Set the reaction temperature and reaction time. After natural cooling to room temperature, wash and dry to obtain the corresponding multi-metal sulfide-expanded graphite composite material.

[0013] Preferably, the ultrasonic power in Step S1 is 100 - 500 W, the ultrasonic time is 10 - 120 min, and the solid-liquid ratio is 50 - 100 mg / ml.

[0014] Preferably, the mixed acid in Step S2 is one or more of nitric acid and hydrochloric acid, sulfuric acid and phosphoric acid, nitric acid and sulfuric acid, or nitric acid and phosphoric acid. The concentration of the mixed acid is 1 - 20 mol / L, the solid-liquid ratio is 50 - 100 mg / ml, the mass ratio of potassium permanganate to expanded graphite is 1:1 - 4, the stirring rate is 100 - 500 r / min, and the stirring time is 1 - 10 h.

[0015] Preferably, the calcination atmosphere in Step S3 is one or more of air, nitrogen, and argon. The calcination temperature is 300 - 1000 °C, and the calcination time is 1 - 8 h.

[0016] Preferably, the ultrasonic power in Step S4 is 100 - 500 W, the ultrasonic time is 10 - 120 min, the organic solvent is one or more of methanol, ethanol, ethylene glycol, or isopropanol, the dosage is 10 - 100 ml, and the solid-liquid ratio is 1 - 100 mg / ml.

[0017] Preferably, the metal salts in Step S5 are one or more of tin salt compounds and cobalt salt compounds, molybdenum salt compounds and cobalt salt compounds, nickel salt compounds and cobalt salt compounds, or zinc salt compounds and cobalt salt compounds. The stirring rate is 100 - 800 r / min, and the stirring time is 1 - 8 h.

[0018] Preferably, the dosage of the thiourea compound in Step S6 is 1 - 10 mmol, the stirring rate is 100 - 800 r / min, the stirring time is 1 - 6 h, the reaction temperature is 100 - 200 °C, and the reaction time is 1 - 30 h.

[0019] In the present invention, by recycling the graphite of the negative electrode of waste lithium-ion batteries, a cross-linked porous three-dimensional expanded graphite matrix is constructed through a controllable expansion strategy, and multi-metal sulfide nanoparticles are in-situ and directionally grown between the layers of expanded graphite by a simple hydrothermal method. The expanded graphite-based bimetallic sulfide nanocomposite material, as an electrode material for lithium-ion batteries, has excellent electrochemical properties, including high specific capacity, excellent rate performance, and cycle stability. This method has a simple process, low cost, and universal applicability. Description of the Drawings

[0020] Figure 1 SEM image of expanded graphite;

[0021] Figure 2 SEM image of Example 1;

[0022] Figure 3 TEM image of Example 1;

[0023] Figure 4 EDS image of Example 1;

[0024] Figure 5 SEM image of Example 2;

[0025] Figure 6 EDS image of Example 2;

[0026] Figure 7 Comparison chart of discharge specific capacity for the first 500 cycles of Example 1 and Comparative Example 1 (0.1 - 3V, 1A);

[0027] Figure 8 Comparison chart of discharge specific capacity for the first 500 cycles of Example 2 and Comparative Example 2 (0.1 - 3V, 1A); Detailed implementation mode

[0028] The preparation method of the expanded graphite-based multi-metal sulfide nanocomposite material is further described in detail below through examples. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention.

[0029] Example 1

[0030] Step S1. Disassemble the discarded ternary battery to remove the negative electrode sheet. After cutting it into small pieces, add deionized water for dispersion and perform ultrasonic treatment for 30 min to separate the graphite material from the copper foil. After filtration, graphite powder is obtained;

[0031] Step S2. Configure a nitric acid-phosphoric acid mixed solution with a ratio of 1:3 in a reaction kettle. Transfer 1 g of waste graphite material to the mixed acid solution, and slowly add 1 g of potassium permanganate thereto under stirring, and continuously stir for 2 h.

[0032] Step S3. Filter and wash the mixed solution to obtain graphite oxide. Place the graphite oxide in a tubular furnace and heat it to 800 °C at a rate of 5 °C / min under N 2 atmosphere, keep it at a constant temperature for calcination for 3 h, and naturally cool it to room temperature to obtain expanded graphite;

[0033] Step S4: Weigh 60 mg of dry expanded graphite powder and ultrasonically disperse it in 45 mL of ethylene glycol solution, and ultrasonically crush it with an ultrasonic crusher for 30 min;

[0034] Step S5: Weigh 0.5 mmol of cobalt nitrate hexahydrate and 1 mmol of zinc nitrate hexahydrate, add them to the solution obtained in Step S4 and stir to dissolve, obtaining a zinc-cobalt bimetallic salt solution;

[0035] Step S6: Weigh 6 mmol of thiourea and add it to the mixed solution in Step S5, and magnetically stir at room temperature for 2 h; then transfer the mixed solution to a 100 mL stainless steel reactor with a polytetrafluoroethylene lining, react at 180 °C for 12 h. After the reaction terminates and the reaction temperature naturally cools to room temperature, wash the obtained black precipitate with water and ethanol multiple times, dry the washed product, and vacuum dry it at 60 °C for 12 h. The corresponding multi-metal sulfide-expanded graphite composite material is obtained.

[0036] Example 2

[0037] Step S1. Disassemble the discarded ternary battery to remove the negative electrode sheet, cut it into small pieces, add deionized water for dispersion, and then ultrasonically treat for 30 min to separate the graphite material from the copper foil. After filtration, graphite powder is obtained;

[0038] Step S2. Prepare a nitric acid-phosphoric acid mixed solution with a ratio of 1:3 in the reactor, transfer 1 g of waste graphite material to the mixed acid solution, and slowly add 1 g of potassium permanganate to it under stirring, and continuously stir for 2 h.

[0039] Step S3. Filter and wash the mixed solution to obtain graphite oxide. Place the graphite oxide in a tubular furnace, heat it to 800 °C at a rate of 5 °C / min under N 2 atmosphere, keep it at a constant temperature and calcine for 3 h, and naturally cool to room temperature to obtain expanded graphite;

[0040] Step S4: Weigh 30 mg of dry expanded graphite powder, ultrasonically disperse it in 45 mL of ethylene glycol solution, and ultrasonically crush it with an ultrasonic crusher for 30 min;

[0041] Step S5: Weigh 1.5 mmol of cobalt nitrate hexahydrate and 1.5 mmol of tin nitrate hexahydrate, add them to the solution obtained in Step S4 and stir to dissolve, obtaining a tin-cobalt bimetallic salt solution;

[0042] Step S6: Weigh 6 mmol of thiourea and add it to the mixed solution in Step S5, and magnetically stir at room temperature for 1 h; then transfer the mixed solution to a 100 mL stainless steel reactor with a polytetrafluoroethylene lining, react at 180 °C for 8 h. After the reaction terminates and the reaction temperature naturally cools to room temperature, wash the obtained black precipitate with water and ethanol multiple times, dry the washed product, and vacuum dry it at 60 °C for 12 h. The corresponding multi-metal sulfide-expanded graphite composite material is obtained.

[0043] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

[0044] Performance Test

[0045] Some of the tests conducted in this experiment were all based on the 2025 model button battery. First, we used the prepared composite material as the negative electrode active material, polyvinylidene fluoride of model 5130 as the binder, conductive carbon black as the conductive agent, and N-methylpyrrolidone as the solvent, and stirred and mixed them in a mass ratio of active material: binder: conductive agent of 7:2:1 until a uniform slurry state was achieved. The prepared negative electrode slurry was evenly coated on the copper foil using a coater, and then transferred to a vacuum drying oven at 80°C for vacuum drying for 12 hours. Calculate the thickness to be achieved for the rolling of the electrode sheet according to the compaction density and perform the rolling treatment. The rolled electrode sheet was cut into electrode sheets with a diameter of 12 mm and uniform thickness using a cutter, and assembled into a button battery in a vacuum glove box. Among them, a lithium sheet was used as the counter electrode, a Celgard 2300 model separator was used, and a lithium hexafluorophosphate-based electrolyte was used.

[0046] Figure 1 It is expanded graphite derived from the negative electrode graphite of waste lithium-ion batteries. It can be seen from the SEM image that it has a worm-like structure.

[0047] Figures 2 - 4 SEM, EDS, and TEM images of Example 1, showing Zn 0.76 Co 0.24 The overall structure of S@EG has a clear three-dimensional sandwich-like structure. Zn 0.76 Co 0.24 S nanoparticles are evenly dispersed into the expanded graphite sheets, with an average size of about 100 nm. Obviously, this special sandwich-like structure can provide an interconnected open structure, which is beneficial to the penetration of the electrolyte in the lithium battery.

[0048] Figures 5 - 6 SEM and EDS images of Example 2, showing that the SnCoS 4 particles have a flower-like structure with a diameter of about 1 μm. Although the particles have a unique sheet-like structure, the dispersibility is poor; adding an appropriate amount of expanded graphite can inhibit the stacking and agglomeration of SnCoS 4 particles, making the multi-layer SnCoS 4It is uniformly loaded on expanded graphite to form an organically bonded whole, improving the stability of its structure; Sn, Co, S, and C elements are uniformly distributed on the surface of expanded graphite.

[0049] Figure 7 It is the cycling performance graph of the products obtained in Comparative Example 1 and Example 1 of the present invention. It can be seen from the graph that at a current density of 1 A g -1 , after 500 long cycles, the capacity of Example 1 can still reach 1086.9 mAh g -1 , the Coulombic efficiency reaches 99.5%, and the capacity retention rate is 89.5%, showing excellent long-cycle durability.

[0050] Figure 8 It is the cycling performance graph of the products obtained in Comparative Example 2 and Example 2. It can be seen from the graph that at a current density of 1 A g -1 , the electrode of Example 2 has excellent electrochemical performance, and the reversible specific capacity is still 1195.90 mAh g after 500 cycles -1 ; while the reversible specific capacity of Comparative Example 2 after 500 cycles is only 535.88 mAh g -1 .

Claims

1. A method for preparing a multimetal sulfide-expanded graphite composite material, characterized in that: The preparation steps are as follows: S1. Disassemble the discarded ternary battery, remove the negative electrode sheet, and collect the materials on the negative electrode sheet by ultrasonic water washing. S2. Prepare a mixed acid solution in a reactor, transfer the waste graphite material into the mixed acid solution, slowly add potassium permanganate into the mixed acid solution while stirring, and continue stirring for a certain period of time. S3. Filter and wash the mixed solution to obtain graphite oxide. Place the graphite oxide in a tube furnace, set the calcination temperature and calcination time under the protection of an inert atmosphere, and naturally cool to room temperature to obtain expanded graphite. S4. Dispersing the expanded graphite in an organic solvent by ultrasonic dispersion. S5. Add a certain amount of metal salt to the solution in step S4 and stir at room temperature for a certain period of time. S6. Weigh a certain amount of thiourea compound and add it to the mixed solution in step S5, and stir it magnetically at room temperature for a certain period of time. Transfer the mixed solution to a stainless steel reactor lined with polytetrafluoroethylene, and transfer the reactor to an oven, set the reaction temperature and reaction time, wait for natural cooling to room temperature, wash and dry, and obtain the corresponding multi-metal sulfide-expanded graphite composite material.

2. The method for preparing a multimetallic sulfide-expanded graphite composite material according to claim 1, characterized in that: The ultrasonic power in step S1 is 100-500 W, the ultrasonic time is 10-120 min, and the solid-liquid ratio is 50-100 mg / ml.

3. The method for preparing a multimetallic sulfide-expanded graphite composite material according to claim 1, characterized in that: The mixed acid in step S2 is one or more of nitric acid and hydrochloric acid, sulfuric acid and phosphoric acid, nitric acid and sulfuric acid, or nitric acid and phosphoric acid, the concentration of the mixed acid is 1-20 mol / L, the solid-liquid ratio is 50-100 mg / ml, the mass ratio of potassium permanganate to expanded graphite is 1:1-4, the stirring rate is 100-500 r / min, and the stirring time is 1-10 h.

4. The method for preparing a multimetal sulfide-expanded graphite composite material according to claim 1, characterized in that: The calcination atmosphere in step S3 is one or more of air, nitrogen, and argon, the calcination temperature is 300-1000° C., and the calcination time is 1-8 hours.

5. The method for preparing a multimetal sulfide-expanded graphite composite material according to claim 1, characterized in that: The ultrasonic power in step S4 is 100-500W, the ultrasonic time is 10-120min, the organic solvent is one or more of methanol, ethanol, ethylene glycol or isopropanol, the dosage is 10-100ml, and the solid-liquid ratio is 1-100mg / ml.

6. The method for preparing a multimetal sulfide-expanded graphite composite material according to claim 1, characterized in that: The metal salt in step S5 is one or more of a tin salt compound and a cobalt salt compound, a molybdenum salt compound and a cobalt salt compound, a nickel salt compound and a cobalt salt compound, or a zinc salt compound and a cobalt salt compound, the stirring rate is 100-800 r / min, and the stirring time is 1-8 h.

7. The method for preparing a multimetal sulfide-expanded graphite composite material according to claim 1, characterized in that: The dosage of the thiourea compound in step S6 is 1-10 mmol, the stirring rate is 100-800 r / min, the stirring time is 1-6 h, the reaction temperature is 100-200° C., and the reaction time is 1-30 h.

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