A resin-based hard carbon anode material, its preparation method and application

Abstract

This invention belongs to the field of hard carbon material preparation technology, specifically involving a resin-based hard carbon anode material and its preparation method and application. Specifically, the process involves: (1) cleaning and drying waste bottles, then cutting them into small pieces; (2) melting and blending the cut material with an ADR chain extender, then pulverizing to obtain particulate material; (3) sintering the above material and then crushing it to obtain hard carbon material. The key to this invention is the addition of an ADR chain extender in the melt blending step. Through the chain extension reaction between the ADR chain extender and the PET end groups, the thermal stability of PET is improved, and melt collapse and excessive graphitization during high-temperature carbonization are suppressed, thereby obtaining a material with a typical hard carbon structure. This invention requires no template, no activator, and no pre-oxidation treatment. The process is simple and environmentally friendly. The resulting hard carbon material has high initial coulombic efficiency and specific capacity, and can be used as a negative electrode material for sodium-ion batteries. Simultaneously, it achieves high-value recycling of waste PET bottles.

Description

Technical Field

[0001] This invention belongs to the field of anode material preparation technology, specifically relating to a resin-based hard carbon anode material, its preparation method, and its application. Background Technology

[0002] Hard carbon materials, due to their large interlayer spacing, rich pore structure, and high sodium / potassium storage capacity, have broad application prospects in sodium-ion batteries, potassium-ion batteries, and supercapacitors. Currently, the precursors for hard carbon are mainly divided into biomass-based, resin-based, and polymer-based types. Waste polyethylene terephthalate (PET) bottles, as a widely available plastic waste with high carbon content and low ash content, have been explored for use in the preparation of carbon materials in recent years. However, the materials obtained by directly carbonizing waste PET are mostly graphite-like carbon or soft carbon materials, whose sodium storage capacity and initial coulombic efficiency are insufficient to meet the requirements of high-energy-density batteries. In existing technologies, to improve the electrochemical performance of carbon materials, template methods, chemical activation methods, heteroatom doping, or pre-oxidation treatments are commonly used. However, these methods generally suffer from problems such as complex processes, severe equipment corrosion, wastewater pollution, high energy consumption, or the involvement of toxic precursors. For PET, it is prone to melting, shrinkage, and graphitization during high-temperature carbonization, making it difficult to directly obtain the ideal hard carbon structure. Currently, there are no reports of using chain extenders to melt-blend and modify waste PET, followed by direct carbonization to prepare hard carbon materials. Therefore, there is an urgent need for a method that is simple, environmentally friendly, requires no templates or activators, and can significantly improve the electrochemical performance of hard carbon. This invention addresses this problem. Summary of the Invention

[0003] This invention addresses the problems of easy melt shrinkage, high degree of graphitization, and difficulty in obtaining ideal hard carbon structures when directly carbonizing waste polyethylene terephthalate (PET) bottles, as well as the shortcomings of existing hard carbon preparation methods such as complex processes, heavy pollution, and high energy consumption. It provides a method for preparing hard carbon materials from waste PET bottles. This method requires no template or activator, is simple to process, and the resulting hard carbon material exhibits high initial coulombic efficiency and specific capacity.

[0004] The specific technical solution of the present invention is as follows: The first aspect of this invention provides a method for preparing a resin-based hard carbon anode material, comprising the following steps: (1) Clean and dry the waste bottles, then cut them into small pieces; (2) The material shredded in step (1) is melt-blended with ADR chain extender, then cooled and removed, and crushed to obtain particulate material; (3) The material in step (2) is sintered and then crushed to obtain hard carbon material.

[0005] Furthermore, in step (1), the waste bottle material is polyethylene terephthalate.

[0006] Furthermore, in step (1), the cleaning solvent is deionized water or alcohol, the drying temperature is 60-120 ℃, and the drying time is 1-12 h.

[0007] Furthermore, in step (2), the ADR chain extender is ADR4468, ADR4366 or ADR4400, the state of the ADR chain extender is granules or powder, and the amount of ADR chain extender added is 0.1wt%-5wt%.

[0008] Furthermore, in step (2), the melt blending temperature is 220 ℃-300 ℃, the melt blending time is 1 min-5 min, and the melt blending instrument is a twin-screw extruder, a single-screw extruder, or a Hack rheometer; the rotation speeds of the melt blending instrument are 50~300 rpm for twin-screw extruder, 30~150 rpm for single-screw extruder, and 10~100 rpm for Hack rheometer. This rotation speed range can ensure uniform mixing of PET and ADR chain extender while avoiding PET molecular chain breakage or thermal degradation due to excessive shearing, thereby effectively achieving chain extension and partial crosslinking.

[0009] Furthermore, in step (2), after the melt blending is completed, the resulting blend is taken out of the equipment and immediately cooled to room temperature by air cooling or water cooling to fix the structure formed by the chain extension reaction and prevent the molecular chains from rearranging or thermally degrading during the slow cooling process; the cooled blend is in the form of blocks, strips or flakes, and is then crushed or granulated to obtain particles with uniform particle size. The crushing method includes, but is not limited to, mechanical crushing, ball milling or cutting crushing.

[0010] Furthermore, in step (3), the sintering treatment is tube furnace sintering, the heating rate is 2~10 ℃ / min, the constant temperature is 1000~1600 ℃, and the constant temperature carbonization time is 1~4 h; the inert atmosphere is selected from at least one of argon, helium or nitrogen.

[0011] Furthermore, the crushing in step (3) is ball milling, with a ball milling speed of 200~800 r / min and a ball milling time of 0.5~8 h, to obtain uniform particles with a particle size of 0.5~15 μm.

[0012] A second aspect of the present invention provides a sodium-ion battery anode comprising a resin-based hard carbon anode material prepared by the above-described preparation method as the anode active material.

[0013] A third aspect of the present invention provides the application of the resin-based hard carbon anode material prepared according to the above-described preparation method in sodium-ion batteries.

[0014] The present invention has the following beneficial effects: (1) This invention is the first to use ADR chain extender for melt blending modification of waste PET bottles, followed by carbonization to prepare hard carbon materials. The ADR chain extender reacts with the terminal hydroxyl and terminal carboxyl groups of PET, which improves the thermal stability of PET and inhibits melt collapse and excessive graphitization during high-temperature carbonization, thereby obtaining a typical hard carbon structure.

[0015] (2) The method of the present invention does not require the use of hard templates, chemical activators, or pre-oxidation treatment, thus avoiding polluting post-treatment steps such as acid washing and alkali washing in traditional methods. The process flow is short, the equipment requirements are low, and the environment is environmentally friendly.

[0016] (3) The hard carbon material obtained by the present invention has high initial coulombic efficiency and specific capacity, and can be directly used as a negative electrode material for sodium-ion batteries.

[0017] (4) This invention uses waste PET bottles as raw materials to realize the high-value utilization of waste plastics, which has both environmental and economic benefits. Attached Figure Description

[0018] Figure 1 The image shows a SEM image of the hard carbon anode material prepared in Comparative Example 1.

[0019] Figure 2 This is a SEM image of the hard carbon anode material prepared in Example 2.

[0020] Figure 3 The first charge-discharge curve of the sodium-ion battery assembled with the hard carbon anode material prepared in Comparative Example 2.

[0021] Figure 4 The constant current cycling curve of the sodium-ion battery assembled with the hard carbon anode material prepared in Comparative Example 2.

[0022] Figure 5 The first charge-discharge curve of the sodium-ion battery assembled with the hard carbon anode material prepared in Example 2.

[0023] Figure 6 The constant current cycling curve is shown for the sodium-ion battery assembled with the hard carbon anode material prepared in Example 2. Detailed Implementation

[0024] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, and instruments used in the embodiments, unless otherwise specified, can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0026] Example 1:

[0027] This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with deionized water, dry them in an 80°C oven for 12 hours, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0028] (2) Weigh 100 g of the above PET fragments, add 0.1 g (0.1 wt%) of ADR4468 chain extender powder, mix evenly and then add to a twin-screw extruder for melt blending. The blending temperature is 220 ℃, the screw speed is 50 rpm, the residence time is 3 min, and after extrusion, water-cooled molding is performed. Then, the chain-extended modified PET particles are obtained by mechanical crushing.

[0029] (3) The modified PET particles obtained in step (2) are placed in a tube furnace and heated to 1000 ℃ at a heating rate of 2 ℃ / min under an argon atmosphere. They are then carbonized at a constant temperature for 4 h and then naturally cooled to room temperature. The product is then taken out and placed in a ball mill for crushing. The ball milling speed is 800 r / min and the ball milling time is 0.5 h.

[0030] The obtained hard carbon negative electrode material, conductive carbon black and binder PVDF were mixed evenly at a mass ratio of 8:1:1, and an appropriate amount of NMP was added as a solvent and stirred evenly. The above slurry was evenly coated on an aluminum sheet with a thickness of 150 mm. Then, the electrode was placed in an 80 ℃ vacuum oven to dry for 8 h and then compacted to make a negative electrode sheet. CR2025 button cells were assembled in an argon-filled glove box, using glass fiber Whatman GF / A as the separator, 1 mol / L NaPF6 DME=100% as the electrolyte, and a sodium metal sheet as the reference electrode.

[0031] The assembled coin cells were tested at 30 °C, with a current density of 0.03 A / g for the first three cycles, followed by a current density of 0.5 A / g. After 500 cycles, the specific capacity was 312 mA h / g, and the initial coulombic efficiency was 72%.

[0032] Example 2:

[0033] This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with alcohol, dry them in a 60 ℃ oven for 3 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0034] (2) Weigh 100 g of the above PET fragments, add 5 g (5 wt%) of ADR4366 chain extender powder, mix evenly and then add to a single screw extruder for melt blending. The blending temperature is 300 ℃, the screw speed is 30 rpm, the residence time is 1 min, and after extrusion, air-cooled molding is formed. Then, the chain-extended modified PET particles are obtained by ball milling.

[0035] (3) The modified PET particles obtained in step (2) were placed in a tube furnace and heated to 1000 ℃ at a heating rate of 2 ℃ / min under a nitrogen atmosphere. The mixture was then carbonized at this temperature for 4 h, and then naturally cooled to room temperature. The resulting product was then placed in a ball mill for crushing at a milling speed of 400 r / min for 5 h. The SEM image of the obtained hard carbon anode material is shown below. Figure 2 As shown.

[0036] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30 °C, with a current density of 0.03 A / g for the first three cycles, and then 0.5 A / g for subsequent cycles. Figure 6 As shown, the specific capacity after 500 cycles is 375 mA h / g. Figure 5 As shown, the initial Coulomb efficiency is 85%.

[0037] Example 3:

[0038] This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with alcohol, dry them in an 80 ℃ oven for 1 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0039] (2) Weigh 100 g of the above PET fragments, add 3 g (3 wt%) of ADR4400 chain extender powder, mix evenly, and then add to the Hacker rheometer for melt blending. The blending temperature is 230℃, the screw speed is 10 rpm, the residence time is 5 min, and after extrusion, the PET particles are air-cooled and then cut and crushed to obtain chain-extended modified PET particles.

[0040] (3) The modified PET particles obtained in step (2) are placed in a tube furnace and heated to 1300 ℃ at a heating rate of 10 ℃ / min under a helium atmosphere. They are then carbonized at a constant temperature for 3 h and then naturally cooled to room temperature. The product is then taken out and placed in a ball mill for crushing. The ball milling speed is 200 r / min and the ball milling time is 8 h.

[0041] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30 °C, with a current density of 0.03 A / g for the first three cycles, followed by a current density of 0.5 A / g. After 500 cycles, the specific capacity was 351 mA h / g, and the initial coulombic efficiency was 77%.

[0042] Example 4:

[0043] This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with deionized water, dry them in an 80 ℃ oven for 12 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0044] (2) Weigh 100 g of the above PET fragments, add 1.5 g (1.5 wt%) of ADR4366 chain extender powder, mix evenly, and then add to the Hacker rheometer for melt blending. The blending temperature is 280 ℃, the screw speed is 100 rpm, the residence time is 2 min, and after extrusion, the PET particles are water-cooled and then cut and crushed to obtain chain-extended modified PET particles.

[0045] (3) The modified PET particles obtained in step (2) are placed in a tube furnace and heated to 1300 ℃ at a heating rate of 5 ℃ / min under an argon atmosphere. They are then carbonized at a constant temperature for 2 h and then naturally cooled to room temperature. The product is then taken out and placed in a ball mill for crushing. The ball milling speed is 500 r / min and the ball milling time is 5 h.

[0046] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30 °C, with a current density of 0.03 A / g for the first three cycles, followed by a current density of 0.5 A / g. After 500 cycles, the specific capacity was 368 mA h / g, and the initial coulombic efficiency was 81%.

[0047] Example 5:

[0048] This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with alcohol, dry them in a 100 ℃ oven for 1 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0049] (2) Weigh 100 g of the above PET fragments, add 0.5 g (0.5 wt%) of ADR4400 chain extender powder, mix evenly and then add to a single screw extruder for melt blending. The blending temperature is 250 ℃, the screw speed is 150 rpm, the residence time is 4 min, and after extrusion, the PET particles are air-cooled and then ball-milled to obtain chain-extended modified PET particles.

[0050] (3) The modified PET particles obtained in step (2) are placed in a tube furnace and heated to 1500 ℃ at a heating rate of 5 ℃ / min under a nitrogen atmosphere. They are then carbonized at a constant temperature for 2 h and then naturally cooled to room temperature. The product is then taken out and placed in a ball mill for crushing. The ball milling speed is 600 r / min and the ball milling time is 3 h.

[0051] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30 °C, with a current density of 0.03 A / g for the first three cycles, followed by a current density of 0.5 A / g. After 500 cycles, the specific capacity was 354 mA h / g, and the initial coulombic efficiency was 82%.

[0052] Example 6:

[0053] This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with alcohol, dry them in a 100 ℃ oven for 1 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0054] (2) Weigh 100 g of the above PET fragments, add 1 g (1 wt%) of ADR4468 chain extender powder, mix evenly and then add to a twin-screw extruder for melt blending. The blending temperature is 280 ℃, the screw speed is 300 rpm, the residence time is 2 min, and after extrusion, the PET particles are water-cooled and then mechanically crushed to obtain chain-extended modified PET particles.

[0055] (3) The modified PET particles obtained in step (2) are placed in a tube furnace and heated to 1400 ℃ at a heating rate of 10 ℃ / min under a helium atmosphere. They are then carbonized at a constant temperature for 4 h and then naturally cooled to room temperature. The product is then taken out and placed in a ball mill for crushing. The ball milling speed is 500 r / min and the ball milling time is 2 h.

[0056] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30 °C, with a current density of 0.03 A / g for the first three cycles, followed by a current density of 0.5 A / g. After 500 cycles, the specific capacity was 336 mA h / g, and the initial coulombic efficiency was 80%.

[0057] Comparative Example 1: This comparative example provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with alcohol, dry them in a 60 ℃ oven for 2 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0058] (2) Weigh 100 g of the above PET fragments.

[0059] (3) The material from step (2) was placed in a tube furnace and heated to 1300 °C at a heating rate of 2 °C / min under an argon atmosphere. It was then carbonized at this temperature for 2 h, and then naturally cooled to room temperature. The resulting product was then placed in a ball mill for crushing at a milling speed of 500 r / min for 2 h. The SEM image of the obtained carbon anode material is shown below. Figure 1 As shown.

[0060] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30°C, with a current density of 0.03 A / g for the first three cycles, followed by a current density of 0.5 A / g. After 500 cycles, the specific capacity was 212 mA h / g, and the initial coulombic efficiency was 63%. Compared with the example, it can be seen that direct sintering of the material results in poor electrochemical performance.

[0061] Comparative Example 2: This embodiment provides a resin-based hard carbon anode material and its preparation method, the specific steps of which are as follows: (1) Collect waste Coca-Cola bottles, remove the caps and labels, clean them with deionized water, dry them in a 100 ℃ oven for 10 h, and then cut the dried PET bottles into pieces with a side length of 2-5 mm.

[0062] (2) Weigh 100 g of the above PET fragments and add them to a twin-screw extruder for processing. The processing temperature is 280℃, the screw speed is 100 rpm, the residence time is 2 min, and after extrusion, the PET fragments are air-cooled and then cut and crushed to obtain chain-extended modified PET granules.

[0063] (3) Place the material from step (2) in a tube furnace and heat it to 1500 ℃ at a heating rate of 2 ℃ / min under an argon atmosphere. Carbonize it at a constant temperature for 2 h, then cool it naturally to room temperature. Take it out and put the obtained product into a ball mill for crushing. The ball milling speed is 500 r / min and the ball milling time is 2 h.

[0064] The obtained hard carbon anode material was assembled into a battery according to the method in Example 1. The coin cell was tested at 30°C, with a current density of 0.03 A / g for the first three cycles, and then a current density of 0.5 A / g for subsequent cycles. Figure 4 As shown, the specific capacity after 500 cycles is 189 mA h / g. Figure 3 As shown, the initial coulombic efficiency is 60%. A comparison with the examples reveals that the electrochemical performance of the material after melt treatment is not significantly improved and may even decrease.

[0065] The specific surface area, average pore size, and interlayer spacing of the materials obtained in Examples 1-6 and Comparative Examples 1-2 were tested, and the specific parameters are shown in Table 1.

[0066] Table 1. Summary of structural parameters of materials in the examples and comparative examples .

[0067] The batteries obtained in Examples 1-6 and Comparative Examples 1-2 were tested for their initial coulombic efficiency and discharge capacity after 500 cycles. The results further demonstrate that the sodium-ion batteries using the hard carbon negative electrode sheet of this application still maintain a high charge and discharge capacity after cycling. See Table 2 for details.

[0068] Table 2 Summary of electrochemical performance of the materials in the examples and comparative examples .

[0069] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A method for preparing a resin-based hard carbon anode material, characterized in that, Follow these steps: (1) Clean and dry the waste bottles, then cut them into small pieces; (2) The material shredded in step (1) is melt-blended with ADR chain extender, then cooled and removed, and crushed to obtain particulate material; (3) The material in step (2) is sintered and then crushed to obtain hard carbon material.

2. The preparation method according to claim 1, characterized in that, In step (1), the waste bottle material is polyethylene terephthalate.

3. The preparation method according to claim 1, characterized in that, In step (1), the cleaning solvent is deionized water or alcohol, the drying temperature is 60-120 ℃, and the drying time is 1-12 h.

4. The preparation method according to claim 1, characterized in that, In step (2), the ADR chain extender is ADR4468, ADR4366 or ADR4400, the ADR chain extender is in the form of granules or powder, and the amount of ADR chain extender added is 0.1wt%-5wt%.

5. The preparation method according to claim 1, characterized in that, In step (2), the melt blending temperature is 220℃-300℃, the melt blending time is 1 min-5 min, and the melt blending instrument is a twin-screw extruder, a single-screw extruder, or a Hack rheometer; the rotation speeds of the melt blending instrument are 50~300 rpm for twin-screw extruder, 30~150 rpm for single-screw extruder, and 10~100 rpm for Hack rheometer.

6. The preparation method according to claim 1, characterized in that, The pulverization method in step (2) includes, but is not limited to, mechanical pulverization, ball milling, or cutting pulverization.

7. The preparation method according to claim 1, characterized in that, In step (3), the sintering process is tube furnace sintering, the heating rate is 2~10 ℃ / min, the constant temperature is 1000~1600 ℃, and the constant temperature carbonization time is 1~4 h; the inert atmosphere is selected from at least one of argon, helium or nitrogen.

8. The preparation method according to claim 1, characterized in that, The crushing in step (3) is done by ball milling, with a ball milling speed of 200~800 r / min and a ball milling time of 0.5~8 h.

9. A sodium-ion battery negative electrode, characterized in that, The resin-based hard carbon anode material prepared by any one of the preparation methods described in claims 1-8 is used as the anode active material.

10. The application of the resin-based hard carbon anode material prepared by any one of claims 1-8 in sodium-ion batteries.

Images