Method and application of graphene@SiO2 composite material produced by molten salt-assisted recycling of wind turbine blades

Abstract

The present invention provides a method and application for preparing a graphene@SiO2 composite material by molten salt-assisted recycling of wind turbine blades, belonging to the technical field of wind turbine blade recycling. The present invention utilizes a simple process, high efficiency, high yield, and rapid molten salt method to successfully recycle waste wind turbine blades and synthesize a graphene@SiO2 composite material. The graphene in the graphene@SiO2 composite material is amorphous and has a thin layered macroscopic morphology, and the macroscopic morphology of silicon dioxide is fibrous with a diameter of 10-20μm. The molten salt used in the present invention provides a reaction system for recycling waste wind turbine blades; the electrode material based on the obtained graphene@SiO2 composite material can be used as a battery negative electrode material. After being used to prepare a sodium ion battery, the sodium ion battery, during the charge and discharge process, can greatly improve the development obstacles of poor conductivity and ion transport performance of pure wind turbine blade powder, and also produce better electrochemical performance in terms of capacity and cycle behavior.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind turbine blade recycling, and in particular relates to a method and application of molten salt-assisted recycling of wind turbine blades to produce graphene@SiO2 composite materials. Background Art

[0002] Wind power generation has become an important part of my country's energy development strategic action plan due to its advantages of cleanliness, high efficiency and renewable energy. my country has become the country with the largest wind power installed capacity in the world. With the advent of the wind turbine retirement wave, retired wind turbine blades have become a large solid waste material that my country urgently needs to solve. Wind turbine blades are mainly made of glass fiber / carbon fiber / plant fiber reinforced composite materials. The reinforcing fiber in wind turbine blades is a high-strength and high-toughness material. The main components of the matrix material are: thermoplastic plastics (polyethylene, polyurethane, polypropylene and polyvinyl chloride) and thermosetting resins (epoxy resin, vinyl ester, polyester). At present, the main recycling methods used for retired wind turbine blades can be divided into the following three categories: (1) mechanical recycling, (2) thermal recycling and (3) chemical recycling. The research team of Tongji University used recycled waste wind turbine blade particles to replace quartz sand in FRP pipes and developed a new type of glass fiber reinforced polymer composite material (glass fiber reinforced polymer) composite pipe. Experimental results using various polar, non-polar, and inorganic solvents by researchers at home and abroad have shown that dichloromethane exhibits excellent swelling properties for epoxy resins, requires minimal use, and maintains low reaction temperatures. However, these recovery methods are cumbersome, involve toxic chemicals, and are inefficient, making them impractical for large-scale resource recovery of retired wind turbine blades. Compared to other recovery methods, molten salts significantly enhance the interaction between reactants because they enhance their fluidity, resulting in reaction rates several times higher than solid-state reactions. Furthermore, molten salts have high solubility, allowing the final product to be removed from the solidified salt by simple washing and filtration. Furthermore, with the advent of the electric vehicle and smart grid era, lithium resource shortages will become a significant constraint to their development. Sodium-ion batteries, with their abundant raw materials and low cost, are gradually becoming a key alternative to lithium-ion batteries. Research on sodium-ion batteries has primarily focused on developing electrode materials and improving battery performance. Research has demonstrated that sodium-ion batteries offer significant advantages in terms of safety and environmental friendliness. Summary of the Invention

[0003] In view of the problems existing in the prior art, the present invention provides a method for preparing graphene@SiO2 composite materials by molten salt-assisted recycling of wind turbine blades and its application. Based on the molten salt method, graphene@SiO2 (graphene-coated SiO2) composite materials are prepared by recycling wind turbine blades. Based on the obtained graphene@SiO2 composite materials, after being compounded with conductive carbon and binder, they are used as electrode materials and applied to negative electrode materials of batteries, such as negative electrode materials of sodium-ion batteries, which can greatly improve the development obstacles of poor conductivity and ion transport performance of pure wind turbine blade powders. It is expected to provide technical support for the future commercial application of synthesizing graphene and silica composite materials by rapidly decomposing and recycling retired wind turbine blades in energy storage batteries.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing graphene@SiO2 composite materials by molten salt-assisted recycling of wind turbine blades, comprising the following steps:

[0006] (1) Mix the molten salt and the wind turbine blade powder evenly to obtain a uniform mixture; the molten salt is one or more of LiCl, KCl, and NaCl;

[0007] (2) React the mixture in an air or nitrogen atmosphere by heating from room temperature to the reaction temperature T to obtain graphene@SiO2 composite materials (black powder).

[0008] The mass ratio of the molten salt to the wind turbine blade powder is (5-20):1.

[0009] The reaction temperature T is: the melting point of the molten salt < T < the boiling point of the molten salt.

[0010] The wind turbine blade includes resin and glass fiber.

[0011] The reaction time is 1 min to 2 h.

[0012] Step (2) also includes washing and drying.

[0013] The heating rate in step (2) is (1-100) °C / min.

[0014] The graphene@SiO2 composite material has a C-coated SiO2 structure, the chemical formula is C@SiO2, the graphene is amorphous, the macroscopic morphology is thin-layered, and the macroscopic morphology of SiO2 is fibrous with a diameter of 10-20 μm.

[0015] The present invention also provides an electrode material based on the above graphene@SiO2 composite material, including the graphene@SiO2 composite material.

[0016] The electrode material further comprises conductive carbon, a binder and a solvent, wherein the mass ratio of graphene@SiO2 composite material:conductive carbon:binder is (5-9):(0.5-3):(0.5-1.5)

[0017] The conductive carbon is one or more of acetylene black, conductive graphite, nanographite, furnace black, Ketjen carbon black and carbon nanotubes.

[0018] The binder is one or more of polyvinylidene fluoride, butyl rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyimide and polytetrafluoroethylene.

[0019] The solvent is one or more of N-methylpyrrolidone, dimethylformamide, tetrahydrofuran, carbon tetrachloride, water and ethanol.

[0020] According to the mass ratio, the solvent: solid matter = (4-12): 1; the solid matter is a graphene@SiO2 composite material and conductive carbon.

[0021] The method for preparing the electrode material comprises the following steps:

[0022] (1) mixing and grinding the graphene@SiO2 composite material and the conductive carbon to obtain a mixture;

[0023] (2) Mixing the binder and the solvent, stirring for 15 minutes to 1 hour, adding the mixture obtained in step (1), and stirring for 8 to 20 hours to form a uniform paste, thereby obtaining an electrode material based on a graphene@SiO2 composite.

[0024] The present invention also provides an electrode plate, comprising a current collector and the above-mentioned electrode material located on the current collector.

[0025] The method for preparing the electrode plate comprises the following steps:

[0026] (1) Coating current collector

[0027] The electrode material is evenly coated on the current collector, dried at 50-80°C for 4 hours, and then placed in a vacuum dryer for 12-20 hours to obtain a dry current collector coated with the electrode material;

[0028] (2) Rolling treatment

[0029] The dried current collector coated with the electrode material is rolled and cut to obtain electrode plates.

[0030] In the step (1), the current collector is copper foil or aluminum foil.

[0031] In the step (1), the drying temperature of the vacuum drying is 50-80°C.

[0032] In the step (1), the active material loading per unit area on the current collector is 0.8 to 5 mg / cm 2 , the active material is a graphene and silicon dioxide composite material and conductive carbon.

[0033] The present invention also provides a working electrode negative electrode, using the electrode plate as the working electrode negative electrode.

[0034] The present invention also provides a battery, comprising the working electrode negative electrode, wherein the battery is a lithium ion battery, a sodium ion battery or a potassium ion battery.

[0035] A method for preparing a sodium ion battery comprises the following steps:

[0036] In an argon environment, the electrode plate is used as a negative electrode and the sodium plate is used as a positive electrode, and the electrode plate, the sodium plate, a diaphragm and an electrolyte are assembled into a sodium ion battery.

[0037] The sodium ion battery of the present invention has a -1 After 500 cycles at a current density of 1.5 GHz, the specific capacity remains at 80-110 mAh g -1 , the capacity retention rate is 100-100.64%. At the same time, at 5000mA g -1 After cycling at a high current density of 100 mA g -1 When the discharge reversible specific capacity is still maintained at 84.4 mAh g -1 .

[0038] The molten salt-assisted recycling of wind turbine blades to prepare a graphene@SiO2 composite material and its application have the following advantages and beneficial effects compared with existing methods for recycling wind turbine blades:

[0039] 1. The present invention successfully recycles waste wind turbine blades using a molten salt method and synthesizes a graphene@SiO2 composite material. The molten salt in the molten salt method provides a reaction system for recycling waste wind turbine blades; the graphene@SiO2 composite material recovered using the molten salt method can be applied in the battery field.

[0040] 2. The present invention's graphene@SiO2 composite material, prepared by molten salt-assisted wind turbine blade powder recovery, has a unique morphology and composition. This wind turbine blade recovery method involves heating from room temperature to (the melting point of the molten salt used to the boiling point of the molten salt used) at a heating rate of (1-100)°C / min, and maintaining the temperature for 1-2 hours. This simple process has low energy consumption and a short reaction time, significantly improving production efficiency. Furthermore, the graphene morphology of the present invention is intact, and its preparation method generates no other byproducts, truly realizing a new, short-process route for the efficient recycling of waste wind turbine blades to directly prepare battery negative electrode material precursors.

[0041] 3. The graphene@SiO2 composite material recovered and prepared by the present invention is used in the negative electrode material of sodium ion batteries. After the sodium ion battery is prepared, during the charge and discharge process, the graphene can greatly improve the development obstacles of the poor conductivity and ion transmission performance of pure wind turbine blade powder, and show excellent long-cycle stability and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 are XRD diagrams, where (a) is the XRD diagram of the wind turbine blade used; (b) is the XRD diagram of the graphene@SiO2 composite material prepared by molten salt assisted technology treatment and recovery.

[0043] Figure 2 are SEM images, where (a) is the SEM image of the wind turbine blade used; and (b) is the SEM image of the graphene@SiO2 composite material prepared by molten salt assisted technology.

[0044] Figure 3 TEM images and energy spectra of graphene@SiO2 composite materials prepared by molten salt-assisted technology treatment and recycling, where (a) is the TEM image of the graphene@SiO2 composite material, (b), (c), and (d) are the element distribution energy spectra of C, O, and Si elements in the graphene@SiO2 composite material, respectively.

[0045] Figure 4 The wind turbine blade powder and the sodium ion battery based on the graphene@SiO2 composite negative electrode material of Example 1 of the present invention are subjected to the conditions of 100, 200, 500, 1000, 2000 and 5000 mA g -1 Rate performance diagram at current density of .

[0046] Figure 5 The sodium ion battery prepared by the wind turbine blade powder and the graphene@SiO2 composite negative electrode material according to Example 1 of the present invention is 100mA g -1 Cycling performance diagram after 500 cycles at a current density of . DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below with reference to the embodiments.

[0048] In the following examples, unless otherwise specified, all raw materials and equipment used were commercially available, and the purity of the raw materials was analytical grade.

[0049] Example 1

[0050] A method for preparing a graphene and silicon dioxide composite material by molten salt-assisted recovery of wind turbine blade powder is as follows:

[0051] The molten salt with a mass ratio of 10:1 was fully mixed with the wind turbine blade powder to obtain a uniform mixture A. The molten salt was a eutectic salt of LiCl and KCl, wherein the mass percentage of LiCl was 59.2%. The mixture A was placed in a 150 mL corundum crucible and heated in a muffle furnace from room temperature to 400 ° C at a rate of 5 ° C min -1 The temperature was maintained at 400°C for 30 minutes. After the heating process was completed, the muffle furnace was cooled to room temperature, and the product was collected directly from the corundum crucible and washed without further treatment. After drying, the graphene@SiO2 composite material was obtained as a black powder with a recovery rate of 50-90%.

[0052] The recycled graphene@SiO2 composite material was subjected to XRD, SEM and TEM test analysis, and its XRD pattern is shown in Figure 1 (b) Yes Figure 1 The XRD pattern in the graphite was analyzed to obtain the chemical formula of the graphene@SiO2 composite material recovered and prepared in this embodiment as C@SiO2. There is a small amount of hexagonal silica (PDF#01-086-1565; space group: P3221) in the wind turbine blade powder, and the calculated lattice parameter value is The graphene@SiO2 composite material synthesized by molten salt-assisted recycling of wind turbine blade powder is amorphous, so there is no obvious characteristic peak intensity in the XRD diagram.

[0053] The SEM images of the wind turbine blade powder and the recycled graphene@SiO2 composite material used in this embodiment are shown in FIG. Figure 2 (a) and (b), from Figure 2 In (a), it can be seen that the silica fiber morphology in the wind turbine blade powder is a fibrous structure with an average diameter of 10-20 μm and resin material exists. Figure 2 In (b), it can be seen that thin layers of graphene and silica fibers exist in the graphene@SiO2 composite material prepared by molten salt recycling.

[0054] The TEM image and energy spectrum of the graphene@SiO2 composite material prepared by molten salt recovery in this example are shown in Figure 3 ,from Figure 3 It can be seen that there is thin layer of graphene in the graphene@SiO2 composite material prepared by molten salt recovery, in which the silicon dioxide particles are coated with graphene. The energy spectrum can show that the thin layer material is graphene and the silicon dioxide is coated with graphene.

[0055] An electrode material based on a graphene@SiO2 composite material comprises the graphene@SiO2 composite material prepared above, conductive carbon, a binder and a solvent; wherein, by mass ratio, the graphene and silicon dioxide composite material: conductive carbon: binder = 7:2:1.

[0056] The conductive carbon is carbon black, the binder is polytetrafluoroethylene, and the solvent is N-methylpyrrolidone.

[0057] The method for preparing the electrode material based on the graphene@SiO2 composite material comprises the following steps:

[0058] Weigh 70 mg of the graphene@SiO2 composite material, 20 mg of carbon black, and 10 mg of polytetrafluoroethylene, and mix and grind the graphene@SiO2 composite material and the carbon black to obtain a mixture;

[0059] 10 mg of polytetrafluoroethylene was added to 400 μL of N-methylpyrrolidone, stirred for 40 minutes, and then added to the above mixture. After magnetic stirring for 10 hours, it became a paste to obtain an electrode material based on graphene@SiO2 composite material.

[0060] An electrode plate includes a current collector and the above-mentioned electrode material located on the current collector. The preparation method includes coating a prepared electrode material based on a graphene@SiO2 composite material on a copper foil, drying it at 60°C for 4 hours, then vacuum drying it at 60°C for 12 hours, rolling it, and cutting it into an electrode plate.

[0061] The electrode plate is used as the negative electrode material of a sodium ion battery.

[0062] The process of assembling the above-mentioned sodium ion battery negative electrode material into a button-type half-cell is as follows:

[0063] The electrode sheets were sliced and pressed, and then assembled into a coin-type half-cell in a glove box with a sodium sheet as the counter electrode. The separator in the coin-type half-cell was a glass microfiber membrane (Whatman, 1823025) and the electrolyte was 1.0M NaPF6 (DIGLYME).

[0064] The assembled button-type half-cell was subjected to rate testing to investigate its cycle stability and rate performance. The rate curve is shown in Figure 4 .from Figure 4As can be seen in the figure, the graphene@SiO2 composite material has a -1 After cycling at a high current density of 100 mA g -1 When the discharge reversible specific capacity is still maintained at 84.4 mAh g -1 , which is significantly higher than that of wind turbine blade powder. This shows that the recycled graphene@SiO2 composite negative electrode material is not significantly damaged after the rapid embedding and extraction process and has good stability.

[0065] This example is based on the sodium ion battery prepared by recycling the prepared graphene@SiO2 composite negative electrode material. The cycle performance of the button-type half-cell prepared at room temperature is shown in the figure. Figure 5 , the results are as follows: at 100mA g -1 After 500 cycles at a current density of 1.5 GHz, the specific capacity remains at 80 mAh g -1 The capacity retention rate is 100.64%, which is significantly higher than that of wind turbine blade powder (49.2 mAh g -1 ).

Claims

1. A method for preparing graphene@SiO2 composite materials from wind turbine blades using molten salt-assisted recycling, characterized in that: It includes the following steps: (1)充分 mix the molten salt and the wind turbine blade powder evenly to obtain a uniform mixture; the molten salt is one or more of LiCl, KCl, and NaCl; (2) React the mixture under a nitrogen atmosphere by heating from room temperature to the reaction temperature T to obtain a graphene@SiO2 composite material; The reaction temperature T is: the melting point of the molten salt < T < the boiling point of the molten salt.

2. The method for preparing graphene@SiO2 composite materials by molten salt-assisted recycling of wind turbine blades according to claim 1, characterized in that: The mass ratio of the molten salt to the wind turbine blade powder is (5~20):

1.

3. The method for preparing graphene@SiO2 composite materials by molten salt-assisted recovery of wind turbine blades according to claim 1, characterized in that: The wind turbine blade includes resin and glass fiber.

4. The method for preparing graphene@SiO2 composite materials by molten salt-assisted recycling of wind turbine blades according to claim 1, characterized in that: The reaction time is 1 min to 2 h.

5. The method for preparing graphene@SiO2 composite materials by molten salt-assisted recycling of wind turbine blades according to claim 1, characterized in that: Step (2) also includes washing and drying.

6. An electrode material, characterized in that: It includes the graphene@SiO2 composite material obtained by the method described in claim 1.

7. An electrode plate, characterized in that: It includes a current collector and the electrode material described in claim 6 located on the current collector.

8. A negative working electrode, characterized in that: Use the electrode sheet described in claim 7 as the working electrode negative electrode.

9. A battery, characterized in that: It includes the working electrode negative electrode described in claim 8, and the battery is a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery.

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