Hard carbon materials, their manufacturing methods, uses, and batteries

Abstract

This invention discloses a hard carbon material, a method for producing the same, its use, and a battery. The method for producing the hard carbon material includes: mixing a solution containing PVC and an aromatic compound under heating conditions until the solvent completely evaporates to obtain a dry gel, wherein the mass ratio of the aromatic compound to the PVC is 2 to 25%; pulverizing, washing, and drying the dry gel to obtain a PVC dehalogenated precursor; carbonizing the PVC dehalogenated precursor to obtain the hard carbon material, wherein the carbonization temperature is 700 to 1200°C and the carbonization time is 1 to 4 hours. The hard carbon material produced by this invention has high atomic efficiency and high electronic conductivity. It also has excellent electrochemical performance when used in battery manufacturing.

Description

[Technical Field]

[0001] This invention claims priority to the following patent applications: one filed on April 30, 2024, with application number 2024105413907, titled "Hard carbon material, method of manufacturing the same, use, and battery"; another filed on April 30, 2024, with application number 2024105413945, titled "Polyvinyl chloride-derived hard carbon material, method of manufacturing the same, use, and battery"; and a third filed on December 16, 2024, with application number 2024118529189, titled "Hard carbon material, method of manufacturing the same, application, and secondary battery."

[0002] This invention specifically relates to hard carbon materials, methods for manufacturing the same, uses, and batteries. [Background technology]

[0003] PVC (polyvinyl chloride) is a widely used plastic material with good chemical stability, corrosion resistance, flame retardancy, and good processing properties. However, environmental and health problems arise during the production, use, and disposal of PVC. Typically, when PVC waste is disposed of in landfills, its poor biodegradability means it remains in the environment for a long time, contaminating soil and groundwater. PVC is not biodegradable under natural conditions and is difficult to recycle. Furthermore, due to its high chlorine content, PVC waste generates chlorine-containing organic substances such as dioxins and highly corrosive HCl during incineration. Therefore, PVC is one of the plastics that causes the greatest harm to the environment.

[0004] PVC, the most representative chlorine-based plastic, is a thermoplastic composed of vinyl chloride monomer through free radical polymerization, with a theoretical chlorine content of 56.8% of its total mass. When PVC is burned or thermally decomposed, it releases carcinogenic organic compounds such as dioxins and furans, along with HCl. In China, the management methods for PVC waste plastics are primarily landfill, incineration, and recycling. The proportions of PVC waste disposed of in landfills, incineration, mechanical recovery, and chemical recovery are 36.0%, 9.3%, 25.5%, and 0.8%, respectively. However, landfills have limited space and lead to serious waste of resources. Furthermore, landfill disposal of PVC waste releases harmful additives, contaminating soil and groundwater. Incineration of PVC waste releases carbon dioxide and HCl, and may also generate polychlorinated dioxins and furans. Additionally, the incinerated residue may contain heavy metals, making it considered hazardous waste.

[0005] Conventional PVC recovery strategies, such as mechanical recovery and processing / reuse, have low economic added value, and material performance deteriorates during the recovery and reuse process, making them unsustainable from a cost perspective. Therefore, current PVC waste treatment technologies cannot achieve reductions in PVC plastic production and manufacturing, improvements in PVC waste treatment rates, or a transformation in PVC consumption patterns. To overcome the shortcomings of conventional recovery strategies, it is necessary to uncover the intrinsic value of plastic waste and urgently develop high-value-added, green resource utilization technologies for halogen-containing polymers such as PVC. In addition to conventional plastic recovery, one of the best methods to reduce pollution from polyvinyl chloride waste is upcycling, which enhances its value and uses it in new applications. Upcycling is a process that transforms waste resources or by-products into new materials with higher value. Chemical upcycling is a more promising alternative method compared to conventional pyrolysis and recovery. This is because chemical upcycling transforms plastic waste into materials and chemicals with high value and multifunctionality, offering greater selectivity and requiring less energy. To achieve the environmental and economic advantages associated with recycling waste plastics, it is necessary to develop effective upcycling technologies to process polyvinyl chloride waste plastics by reducing their chlorine content while converting and upgrading them into high-value, multi-functional chemicals.

[0006] Globally, concerns about energy and environmental problems stemming from the burning and depletion of fossil fuel resources are increasing daily, leading to a growing interest in exploring highly efficient and renewable energy sources. Therefore, research and development of various advanced electrochemical energy storage and conversion devices are underway to achieve sustainable development. While the operating principles of energy storage and conversion systems differ, a crucial prerequisite for developing high-performance devices is the search for suitable electrode materials with ideal components and structures. Among the electrode materials already developed, carbon-based materials are attracting attention due to their advantages such as high conductivity, good chemical stability, and structural stability. While carbon-based electrode materials show promising potential, conventional carbon materials are all manufactured using fossil fuels as synthesis raw materials, making them harmful to the environment and resulting in high costs. Therefore, the development of suitable precursors that are abundant in resources and have minimal environmental impact is being actively pursued. From the perspective of sustainable development, using plastic waste as a precursor for carbon synthesis can be considered a way to transform waste into treasure.

[0007] One of the most promising applications of upcycling polyvinyl chloride waste is the production of high-value carbon-based electrode materials for energy storage, such as hard carbon. Hard carbon is a carbon material with a high degree of graphitization, high conductivity, and high stability, and is widely used in fields such as lithium-ion batteries, supercapacitors, and fuel cells. With the rapid development of new energy fields and the electronic information industry, the need for high-performance hard carbon materials is expanding. Currently, precursors for hard carbon include biomass, coal, and sugars, but the cost of raw materials is high. Therefore, if waste polymers can be fully utilized as a carbon source, the cost of raw materials for hard carbon production will be significantly reduced.

[0008] Hard carbon, used as the negative electrode material for alkali metal ion batteries, has an internal spiral layer structure composed of twisted and curved carbon layers, resulting in a large interlayer distance. Due to its unique turbostratic structure, hard carbon has advantages such as high theoretical capacity, high rate performance, and excellent cycle performance. However, it should be noted that the highly disordered structure of hard carbon can slow down the kinetic rate of solid-state diffusion of lithium ions, potentially leading to low conductivity and insufficient ion diffusion capacity. As a result, actual capacity and rate performance are limited, and the initial Coulomb efficiency is low. Furthermore, the electrochemically inert interface and disordered structure unique to hard carbon slow down the diffusion of lithium ions and electrons, potentially leading to a decrease in rate capacity and deterioration of long-term cycle stability. Therefore, in order to effectively improve rate performance and long-term cycle stability, it is important to design an appropriate hard carbon interface structure to improve ion transport performance and provide a highly efficient diffusion network.

[0009] Normally, thermoplastic polyvinyl chloride is converted into disordered hard carbon consisting of wound, twisted, and folded carbon layers in an inert atmosphere. However, due to its highly disordered structure, various defects and voids are generated internally. In the highly disordered structure of hard carbon, the kinetic rate of solid diffusion of lithium ions slows down, potentially leading to low conductivity and insufficient ion diffusion capacity. As a result, the actual capacity and rate performance are limited, and the initial Coulomb efficiency is low. Therefore, the following challenges exist when using it as a negative electrode material for batteries.

[0010] (i) Polyvinyl chloride has a low carbon atom economy in the carbonization process (approximately 33 at.%), so it needs to be improved to minimize the generation of gaseous and liquid by-products and to obtain more carbon-based solid products.

[0011] (ii) It is necessary to improve the initial Coulomb efficiency by rationally designing and controlling the conductivity, interlayer distance, and porous structure of polyvinyl chloride-derived carbon to reduce the charge transfer energy barrier.

[0012] (iii) It is necessary to functionalize and design carbon derived from polyvinyl chloride to enhance its value. This is to maximize the benefits of halogen-containing plastic recycling by establishing a "mass production reduction - recovery - upcycling" route through the realization of PVC upcycling. [Overview of the project]

[0013] The technical problem that this invention aims to solve is, in one aspect, to overcome the drawbacks of conventional thermoplastic polyvinyl chloride, which has low atomic efficiency, poor electronic conductivity, and poor electrochemical performance when used to manufacture hard carbon materials, and to provide a hard carbon material, a method for manufacturing the same, its use, and a battery. The hard carbon material manufactured by this invention has high atomic efficiency and high electronic conductivity. It also has excellent electrochemical performance when used in battery manufacturing.

[0014] Further improvements in the overall performance of PVC-derived carbon anodes are urgently needed, with the key points being the construction of energy storage active sites, adjustment of pore structure, and improvement of conductivity. In this invention, polyvinyl chloride waste is upcycled into a highly conductive polyvinyl chloride-based hard carbon material having a slit / micropore-filled structure by using PVC as a raw material and combining a simple and easy-to-implement solvent wet treatment with an automated chemical vapor deposition system. By grafting aromatic compounds onto the carbon chains of the PVC polymer through a high-temperature elimination reaction between H in the aromatic compound and Cl in PVC, sp 2-The C content is increased. Furthermore, the benzene ring structure, which readily adheres to the slit pore walls of PVC-derived carbon, deposits locally at high temperatures to form thin layers of graphene-like nanodomains, providing additional energy storage sites through a void-filling mechanism. Moreover, because benzene rings have high thermal stability, they tend to be easily adsorbed onto the slit pore walls inside PVC-derived carbon due to the action of van der Waals forces between the π orbitals of the carbon plane on the pore wall and the electron density inside the benzene ring. The adsorbed material is decomposed by the catalytic action of the pore wall to form a large number of flattened, thin layers of graphene nanodomains, which deposit and grow until benzene ring molecules can no longer enter the voids. More importantly, during the thermal decomposition process of PVC, the crystalline domains of the nanographene carbon layer obtained by rearrangement and growth block the gas transport pathway, limiting the diffusion of benzene vapor and the release of HCl during the thermal decomposition process of PVC. As a result, a large number of closed slit pores and micropores are formed in the PVC-derived carbon. These slit pores and micropores can provide additional storage sites for ions through a void-filling mechanism. The structural design concept of embedding a small number of graphene-like nanodomains within the open voids of the carbon material provided in this patent significantly improves the storage performance of adsorbed and intercalated lithium.

[0015] The present invention solves the above technical problems through the following technical solutions.

[0016] The present invention provides a method for producing a hard carbon material, comprising the following steps.

[0017] (1) A solution containing PVC and an aromatic compound is mixed under heating conditions until the solvent completely evaporates to obtain a dry gel. The mass ratio of the aromatic compound to the PVC is 2-25%.

[0018] (2) The dried gel is crushed, washed, and dried to obtain a PVC dehalogenated precursor.

[0019] (3) The PVC dehalogenated precursor is carbonized to obtain the hard carbon material. The carbonization temperature is 700 to 1200°C, and the carbonization time is 1 to 4 hours.

[0020] In step (1), the viscosity number K value of the PVC may be 50 to 80, preferably 55 to 70.

[0021] In the present invention, when the aromatic compound contains a halogen, a high-temperature elimination reaction occurs between H in the aromatic compound and Cl in the PVC, as well as a high-temperature elimination reaction occurs between Cl in the aromatic compound and H in the PVC.

[0022] In step (1), in accordance with the conventions of the art, the aromatic compound is generally a compound containing at least one benzene ring, and is preferably an aromatic hydrocarbon and / or an aromatic hydrocarbon derivative.

[0023] The aforementioned aromatic hydrocarbons are generally hydrocarbon compounds containing a benzene ring, and include monocyclic aromatic hydrocarbons and / or polycyclic aromatic hydrocarbons. The aforementioned monocyclic aromatic hydrocarbons are generally hydrocarbon compounds containing only one benzene ring, such as benzene or toluene. The aforementioned polycyclic aromatic hydrocarbons are generally hydrocarbon compounds having at least two or more benzene rings, and include non-condensed ring aromatic hydrocarbons (e.g., biphenyl) and / or condensed ring aromatic hydrocarbons (e.g., naphthalene).

[0024] Preferably, the aromatic hydrocarbon derivative is an aromatic acid and / or a halogenated aromatic hydrocarbon. The aromatic acid is, for example, benzoic acid. The halogen in the halogenated aromatic hydrocarbon may be one or more of F, Cl, Br, and I, preferably Cl. The number of halogen atoms in the halogenated aromatic hydrocarbon is at least 1. The halogenated aromatic hydrocarbon may be a side-chain halogenated aromatic hydrocarbon and / or an aromatic ring halogenated aromatic hydrocarbon. The side-chain halogenated aromatic hydrocarbon is one in which the halogen is bonded to a carbon atom of the side chain of the aromatic ring, and the aromatic ring halogenated aromatic hydrocarbon is one in which the halogen is bonded to a carbon atom of the aromatic ring. The aromatic ring halogenated aromatic hydrocarbon may be, for example, chlorobenzene or 1,2-dichlorobenzene.

[0025] In step (1), the mass ratio of the aromatic compound to the PVC is, for example, 5%, 9%, 12%, or 18%, and preferably 7% to 15%.

[0026] In step (1), the solvent in the solution may be any solvent that is commonly used in the field to dissolve PVC, such as NMP.

[0027] In step (1), the ratio of the mass of the PVC to the volume of the solvent in the solution may be 1:(20~40) g / mL, for example, 1:30 g / mL.

[0028] In step (1), the method for producing a solution containing the PVC and aromatic compound preferably includes a process of stirring and mixing the PVC and solvent at room temperature until the PVC is completely dissolved, and then adding the aromatic compound.

[0029] In step (1), the mixing method may be one that is common in the field, for example, stirring.

[0030] In step (1), the mixing temperature is preferably 140 to 180°C, for example, 150°C.

[0031] In step (1), the mixing process preferably includes first stirring the solution containing the PVC and aromatic compound at 60-90°C for 1-3 hours to obtain a sol, and then stirring the sol at 140-180°C until the solvent is completely evaporated to obtain a dry gel.

[0032] In step (2), the cleaning operation and conditions may be those common in the field, for example, cleaning with ethanol and water.

[0033] In step (2), the drying operation and conditions may be those that are common in the art.

[0034] In step (3), preferably, before carbonization, the PVC dehalogenation precursor is first pulverized into a powder.

[0035] In step (3), the carbonization is generally carried out under a protective atmosphere that does not react with the reaction system, for example, under nitrogen gas or an inert gas. The inert gas is, for example, argon gas.

[0036] The flow velocity when introducing the protective atmosphere may be 100 to 500 sccm, preferably 200 to 400 sccm, for example, 300 sccm.

[0037] In step (3), the carbonization is generally carried out in a tubular furnace.

[0038] In step (3), the carbonization temperature is preferably 700 to 900°C, for example, 800°C. Preferably, the carbonization time is 1 to 3 hours, for example, 2 hours. The heating rate to the carbonization temperature may be 2 to 10°C / min, for example, 5°C / min. After the completion of carbonization, the process further includes a cooling process to allow the temperature to naturally decrease to room temperature.

[0039] The present invention further provides a hard carbon material produced by the above-described production method.

[0040] In the present invention, preferably, the hard carbon material has a few-layer graphene-like carbon layer structure inside. Generally, the few-layer graphene-like carbon layer is a material composed of 2 to 10 layers of graphene nanosheets. Preferably, the few-layer graphene-like carbon layer structure is distributed on the slit pore walls inside the hard carbon material.

[0041] In the present invention, the graphite interlayer distance of the hard carbon material may be 0.340 to 0.385 nm. Generally, the graphite interlayer distance is the interlayer distance d calculated by Bragg's law based on the results of XRD measurement. 002 is.

[0042] In the present invention, the pore size distribution range of the hard carbon material may be 0.1 to 6 nm, and preferably, it is 2 to 4 nm.

[0043] In the present invention, the specific surface area of the hard carbon material may be 1 to 5 m 2 / g, for example, 1.15 m 2 / g, 1.2 m 2 / g or 1.25 m 2 / g, and preferably, it is 1.2 to 1.3 m 2 / g.

[0044] In the present invention, preferably, the I D / I G is 0.948 to 1.05, for example, 0.951 or 1.024, and more preferably, it is 1.0 to 1.03. The I D / I G is the intensity ratio of the D peak to the G peak.

[0045] In the present invention, the conductivity of the hard carbon material is 1.14 to 5 S m -1It may also be, for example, 1.158, 1.198, 1.206 or 1.721, preferably 1.18 to 1.22S m -1 That is the case.

[0046] In the present invention, preferably, the hard carbon material has a current density of 50 mA g -1 The reversible ratio capacity at that time is 355-600mAh g -1 For example, 362.5mAh g -1 , 436.5mAh g -1 , 552.6mAh g -1 or 553.8mAh g -1 That is the case.

[0047] In the present invention, preferably, the hard carbon material has a current density of 50 mA g -1 The initial Coulomb efficiency in this case is 70-85%.

[0048] In the present invention, preferably, the hard carbon material has a current density of 0.5 A g -1 The reversible ratio capacity at that time is 440~540mAh g -1 And more preferably, 510~540mAh g -1 That is the case.

[0049] In the present invention, preferably, the hard carbon material has a current density of 0.5 A g -1 The capacity retention rate after 300 cycles in that case is 99% or higher.

[0050] In the present invention, preferably, the hard carbon material has a current density of 1.5 A g -1 The reversible ratio capacity at that time is 120~210mAh g -1 And more preferably, 190~210mAh g -1 That is the case.

[0051] In the present invention, preferably, the hard carbon material has a current density of 1.5 A g -1 The capacity retention rate after 1800 cycles is 99% or higher.

[0052] The present invention further provides the use of the hard carbon material described above in batteries.

[0053] The present invention further provides a battery comprising the hard carbon material described above.

[0054] In the present invention, preferably, the battery is a lithium-ion battery or a sodium-ion battery.

[0055] Assuming that they conform to common sense in the field, any combination of the above preferred conditions can yield any of the preferred embodiments of the present invention.

[0056] All reagents and raw materials used in this invention can be obtained through commercial channels.

[0057] The positive and progressive effects of this invention are as follows:

[0058] (1) The hard carbon material produced by this invention has high atomic efficiency and high electronic conductivity. It also has excellent electrochemical properties when used in battery manufacturing.

[0059] (2) The manufacturing method of the present invention is simple, low-cost, and advantageous for industrial production.

[0060] (3) The PVC-derived carbon produced by the present invention has an improved carbon atom efficiency from 33% to 70% or more.

[0061] (4) In this invention, by adjusting the structure of polyvinyl chloride-derived hard carbon by introducing aromatic compounds, the growth of a small number of graphene-like nanocrystalline domains inside the polyvinyl chloride-derived hard carbon can be promoted, thereby improving electronic conductivity. Furthermore, it is possible to improve the specific capacity of the polyvinyl chloride-derived hard carbon anode and to improve the initial Coulomb efficiency to some extent.

[0062] The technical problem to be solved in the second aspect of the present invention is to overcome the drawbacks of the prior art, which exist in PVC-based hard carbon materials, such as their inferior rate performance and long-term cycle stability, and to provide a polyvinyl chloride-derived hard carbon material, a method for producing the same, its use, and a battery. The hard carbon material produced by the present invention has a larger specific surface area, a larger interlayer distance, and a more developed ion / electron conduction network, and therefore has excellent electrochemical performance when used in a battery, and in particular has desirable rate performance and long-term cycle stability.

[0063] In this invention, the degree of defects inside the hard carbon is effectively controlled by first heating and melting PVC powder and thermoplastic resin, followed by pre-dehalogenation at low temperatures and carbonization with the assistance of inorganic salts. This produces a hard carbon material with a larger specific surface area, larger interlayer distance, a more developed ion / electron conduction network, and superior electrochemical performance. Pre-dehalogenation at low temperatures achieves partial dehalogenation of the PVC. Abundant active carbon chains and active carbon chains of the thermoplastic resin aggregate on the partially dehalogenated polyvinyl chloride polymer, promoting the subsequent formation of highly conductive carbon. In the subsequent high-temperature carbon layer rearrangement process with the assistance of inorganic halide salts, the HCl gas flow generated by the continuous dechlorination of the pre-dehalogenated PVC precursor impacts the internal structure, forming a dense, disordered turbostratic structure and closed voids inside. Furthermore, the presence of the molten inorganic halide salt induces rearrangement of the surface carbon layer, forming an ordered graphene carbon layer. Inorganic halide salt crystals act as templates and encapsulants for graphene growth, agglomerating carbon atoms at grain boundaries to prevent HCl release. These carbon atoms then serve as nucleation centers for the growth of vertically oriented graphene layers.

[0064] The present invention solves the above technical problems through the following technical solutions.

[0065] This invention provides a method for producing a polyvinyl chloride-derived hard carbon material. The production method includes the following steps.

[0066] (1) PVC powder and thermoplastic resin are heated and melted, and after cooling, substance A is obtained. Next, a pre-dehalogenation reaction is performed on substance A under inert gas shielding to obtain a pre-dehalogenated sample. The thermoplastic resin is polypropylene and / or polyethylene. The mass ratio of the thermoplastic resin to the PVC powder is 5 to 50%. The temperature of the pre-dehalogenation reaction is 250 to 500°C, and the duration of the pre-dehalogenation reaction is 1 to 5 hours.

[0067] (2) The pre-dehalogenated sample is covered with an inorganic halide salt in a reaction tube, the reaction tube is evacuated and sealed, and then carbonized, washed and dried to obtain the polyvinyl chloride-derived hard carbon material. The mass ratio of the inorganic halide salt to the pre-dehalogenated sample is (1.2~4.5):1. The carbonization temperature is above the melting point of the inorganic halide salt, and the carbonization time is 5~20h.

[0068] In step (1), the viscosity number K value of the PVC powder may be 50 to 80, preferably 55 to 70.

[0069] In step (1), the melt flow index of the polypropylene may be 10 to 40 g / 10 min, for example, 35 g / 10 min.

[0070] In step (1), the melt flow index of the polyethylene may be 10 to 40 g / 10 min, for example, 25 g / 10 min.

[0071] In step (1), preferably, the mass ratio of the thermoplastic resin to the PVC powder is 5 to 20%, for example, 10%.

[0072] In step (1), the heating and melting is generally carried out in a heating furnace. The heating furnace may be a type common in the field, for example, a tubular furnace. The heating and melting is generally carried out in an inert atmosphere (for example, argon gas).

[0073] In step (1), the heating and melting temperature may be 100 to 140°C, for example, 120°C.

[0074] In step (1), the heating and melting time may be 1 to 4 hours, for example, 2 hours.

[0075] In step (1), the type of inert gas may be one that is common in the field, for example, argon gas.

[0076] In step (1), the flow rate when introducing the inert gas may be 100 to 500 sccm, preferably 200 to 400 sccm, for example, 300 sccm.

[0077] In step (1), the pre-dehalogenation reaction is generally carried out in a tubular furnace.

[0078] In step (1), the temperature of the pre-dehalogenation reaction is preferably 300 to 400°C, for example, 360°C.

[0079] In step (1), the duration of the pre-dehalogenation reaction is preferably 1 to 3 hours, for example, 2 hours.

[0080] In step (1), preferably, the rate of heating up to the temperature of the pre-dehalogenation reaction is 2 to 10°C / min, for example, 5°C / min.

[0081] Step (1) generally includes a process of allowing the temperature to naturally cool to room temperature after the completion of the pre-dehalogenation reaction.

[0082] In step (1), after the pre-dehalogenation reaction is completed, it is preferably necessary to further wash and dry the pre-dehalogenated sample.

[0083] The solvent used for the cleaning may be one that is common in the field, for example, water and / or anhydrous ethanol. When the solvent used for the cleaning is a mixed solution of water and anhydrous ethanol, preferably the volume ratio of water to anhydrous ethanol is (1 to 5):1, for example, 3:1.

[0084] In step (2), the reaction tube may be one that is common in the field, for example, a quartz glass test tube.

[0085] In step (2), after the vacuum evacuation, preferably the vacuum level of the reaction tube is 10 -2 It will be less than or equal to mbar.

[0086] In step (2), preferably, the melting point of the inorganic halide salt is 700°C or higher.

[0087] In step (2), preferably, the cation of the inorganic halide salt comprises one or more of alkali metals, alkaline earth metals, and transition metals, and more preferably, an alkali metal.

[0088] Preferably, the alkali metal includes Na and / or K.

[0089] Preferably, the alkaline earth metal includes one or more of Mg, Ca, Sr, and Ba.

[0090] Preferably, the transition metal includes one or more of Fe, Co, Ni, Cu, and Zn.

[0091] In step (2), preferably, the anion of the inorganic halide salt comprises one or more of Cl ions, Br ions, and I ions, and more preferably, Cl ions or Br ions.

[0092] In step (2), preferably, the inorganic halide salt is one or more of NaCl, KCl, and NaBr.

[0093] In step (2), preferably, the mass ratio of the inorganic halide salt to the pre-dehalogenated sample is (1.5 to 3.5):1, for example, 2:1, 2.5:1, or 3.5:1.

[0094] In step (2), preferably, the carbonization temperature is 10 to 200°C higher than the melting point of the inorganic halide salt.

[0095] In step (2), the carbonization time is preferably 5 to 15 hours, for example, 10 hours.

[0096] When the inorganic salt is NaCl, the carbonization temperature is preferably 810 to 1000°C, for example, 820°C, 850°C, 900°C, or 950°C.

[0097] When the inorganic salt is NaBr, the carbonization temperature is preferably 780 to 900°C, for example, 800°C.

[0098] When the inorganic salt is KCl, the carbonization temperature is preferably 800 to 1000°C, for example, 820°C.

[0099] In step (2), preferably, the heating rate to the carbonization temperature is 2 to 10°C / min, for example, 5°C / min.

[0100] In step (2), the solvent used for cleaning may be one that is common in the field, for example, water and / or anhydrous ethanol. When the solvent used for cleaning is a mixed solution of water and anhydrous ethanol, preferably the volume ratio of water to anhydrous ethanol is 1:(1~5), for example, 1:3.

[0101] In step (2), preferably, the material is further crushed after drying.

[0102] The present invention further provides a polyvinyl chloride-derived hard carbon material manufactured by the manufacturing method described above.

[0103] In the present invention, preferably, the exterior of the polyvinyl chloride-derived hard carbon material is coated with a continuous, small number of graphene-carbon layers. Generally, the small number of graphene-like carbon layers is a material consisting of 2 to 10 layers of graphene nanosheets. Preferably, the number of layers of the small number of graphene-carbon layers is less than 5.

[0104] In the present invention, the graphite interlaminar distance of the polyvinyl chloride-derived hard carbon material may be 0.352 to 0.40 nm, preferably 0.352 to 0.38 nm, for example, 0.354 nm, 0.358 nm, or 0.361 nm. Generally, the graphite interlaminar distance is the interlaminar distance d calculated by Bragg's law based on the results of XRD measurement. 002 That is the case.

[0105] In the present invention, the pore size distribution range of the polyvinyl chloride-derived hard carbon material may be 7.5 to 15 nm, preferably 8 to 12 nm, for example, 8.2 nm, 9 nm, or 10.5 nm.

[0106] In the present invention, the specific surface area of ​​the polyvinyl chloride-derived hard carbon material is 4.8 to 15 m². 2 It may be / g, preferably 5-10m 2 It is / g, for example, 5.8m 2 / g, 6.5m2 / g or 7.5m 2 It is / g.

[0107] In the present invention, preferably, the polyvinyl chloride-derived hard carbon material I D / I G The value is 0.94 to 1.05, for example, 0.948, 0.965 or 0.991, and more preferably 0.955 to 0.98. D / I G This is the intensity ratio of the D peak to the G peak.

[0108] The present invention further provides the use of the above-mentioned polyvinyl chloride-derived hard carbon material in batteries.

[0109] The present invention further provides a battery comprising the above-mentioned polyvinyl chloride-derived hard carbon material.

[0110] In the present invention, preferably, the battery is a lithium-ion battery or a potassium-ion battery.

[0111] Assuming that they conform to common sense in the field, any combination of the above preferred conditions can yield any of the preferred embodiments of the present invention.

[0112] All reagents and raw materials used in this invention can be obtained through commercial channels.

[0113] The positive and progressive effects of this invention are as follows:

[0114] (1) The hard carbon material produced by the present invention has a larger specific surface area, a larger interlayer distance, and a more developed ion / electron conduction network, and therefore exhibits excellent electrochemical performance as an anode material for lithium-ion batteries and potassium-ion batteries, and in particular has favorable rate performance and long-term cycle stability.

[0115] (2) The carbon yield of the hard carbon material produced by the present invention reaches 26-33%.

[0116] (3) The manufacturing method of the present invention is simple, low-cost, and advantageous for industrial production.

[0117] (4) The present invention provides a new solution for upcycling halogen-based waste plastics, and by extending the design of electrode materials for lithium-ion batteries and potassium-ion batteries to include waste plastic resources, it is possible to improve resource utilization efficiency and realize sustainable development.

[0118] The technical problem to be solved in the third aspect of the present invention is to overcome the drawbacks of conventional technology, namely that halogen-containing waste polymer materials cannot be fully utilized and that the raw material cost of hard carbon is soaring, and to provide a hard carbon material, a method for producing the same, its use, and a secondary battery. The manufacturing method of the present invention realizes a pollution-free treatment of halogen-containing polymer waste and enables high value-added utilization, and has advantages such as being efficient, environmentally friendly, green, and energy-saving. Furthermore, when the manufactured hard carbon material is used in a battery, it has excellent specific capacity and rate performance.

[0119] This invention relates to a hard carbon material manufacturing process that uses a halogen-containing polymer as a raw material. First, a mixture is obtained by heating and melting the halogen-containing polymer and a thermoplastic resin (polypropylene, polyethylene). Since the thermoplastic resin can coat the halogen-containing polymer, the situation where HCl is released during the subsequent dehalogenation process of the halogen-containing polymer and the pore size increases is avoided. The halogen-containing polymer and reducing metals (alkali metals, alkaline earth metals) in the mixture first form a salt with a carbon-containing precursor through a dehalogenation reaction. This removes the halogen from the halogen-containing polymer and then carbonizes the carbon-containing precursor, thereby producing a hard carbon material with excellent electrochemical performance. During the dehalogenation reaction, the reducing metal promotes a more complete dehalogenation reaction of the halogen-containing polymer and fixes highly contaminating halogen atoms. The reducing metal and the resulting salts permeate the partially carbonized polymer as a template or pore-forming agent. This enables higher specific capacity and rate performance when used as a high-performance negative electrode in sodium / lithium-ion batteries. This manufacturing method enables the treatment of halogen-containing polymer waste without releasing pollution, while also enabling high-value-added utilization. It has advantages such as being efficient, environmentally friendly, green, and energy-saving.

[0120] The present invention solves the above technical problems through the following technical solutions.

[0121] This invention provides a method for manufacturing hard carbon materials. The manufacturing method includes the following steps.

[0122] A halogen-containing polymer powder and a thermoplastic resin are mixed, heated and melted, and the mixture is obtained after cooling. Next, the mixture is mixed with a reducing metal, and dehalogenation is performed by heating at 100-400°C for 2-12 hours under an inert gas shield to obtain a dehalogenated sample. Then, the dehalogenated sample is washed, dried, and carbonized to obtain a hard carbon material.

[0123] The thermoplastic resin is polypropylene and / or polyethylene, and the mass ratio of the thermoplastic resin to the halogen-containing polymer powder is 2 to 10%.

[0124] When the reducing metal is an alkali metal in its elemental form, the molar ratio of halogen atoms to the reducing metal in the halogen-containing polymer powder is 1:(1~3).

[0125] When the reducing metal is an alkaline earth metal in its elemental form, the molar ratio of halogen atoms in the halogen-containing polymer powder to the reducing metal is 1:(0.5~1.5).

[0126] In the present invention, preferably, the halogen-containing polymer powder is polyvinyl chloride (PVC) and / or polyvinylidene chloride (PVDC). The particle size of the halogen-containing polymer powder may be 0.1 to 1 μm. As the halogen-containing polymer powder, powder obtained by washing and mechanically grinding waste halogen-containing polymer products may be used.

[0127] The viscosity number K value of the polyvinyl chloride may be 50 to 80, for example, 62 to 60.

[0128] In the present invention, the melt flow index of the polypropylene may be 10 to 40 g / 10 min, for example, 35 g / 10 min.

[0129] In the present invention, the melt flow index of the polyethylene may be 10 to 40 g / 10 min, for example, 25 g / 10 min.

[0130] In the present invention, preferably, the mass ratio of the thermoplastic resin to the halogen-containing polymer powder is 2 to 8%, for example, 5%.

[0131] In the present invention, the heating and melting is generally carried out in a heating furnace. The heating furnace may be a type common in the art, for example, a tubular furnace. The heating and melting is generally carried out in an inert atmosphere (for example, argon gas).

[0132] In the present invention, the heating and melting temperature may be 100 to 140°C, for example, 120°C.

[0133] In the present invention, the heating and melting time may be 1 to 4 hours, for example, 2 hours.

[0134] In the present invention, preferably, the alkali metal element is Na and / or K.

[0135] In the present invention, preferably, the alkaline earth metal element is one or more of Mg, Ca, and Ba.

[0136] In the present invention, preferably, when the reducing metal is an alkali metal in elemental form, the molar ratio of halogen atoms in the halogen-containing polymer powder to the reducing metal is 1:(1~2), for example, 1:1.1, 1:1.2, or 1:1.3.

[0137] In the present invention, preferably, when the reducing metal is an alkaline earth metal element, the molar ratio of halogen atoms in the halogen-containing polymer powder to the reducing metal is 1:(0.5~1), for example, 1:0.55.

[0138] In the present invention, the temperature of the heating dehalogenation is preferably 200 to 400°C, for example, 250°C.

[0139] In the present invention, the heating dehalogenation time is preferably 2 to 6 hours, for example, 3 hours.

[0140] In the present invention, the heating dehalogenation is generally carried out in a tubular furnace.

[0141] In the present invention, the inert gas may be one that is common in the field, for example, nitrogen gas or argon gas.

[0142] In the present invention, the cleaning operation and conditions may be those that are common in the art, for example, cleaning is performed using a mixed solution of deionized water and anhydrous ethanol. In the mixed solution, the volume ratio of deionized water to anhydrous ethanol may be 3:1.

[0143] In the present invention, the drying operation and conditions may be those that are common in the art.

[0144] In the present invention, in accordance with the conventions of the art, the carbonization is generally carried out under an inert gas atmosphere, such as nitrogen gas or argon gas.

[0145] In the present invention, the carbonization temperature is preferably 600 to 1000°C, for example, 800°C, 850°C, or 900°C.

[0146] In the present invention, the carbonization time may be 0.5 to 10 hours, preferably 3 to 6 hours, for example, 4 hours.

[0147] The present invention further provides a hard carbon material manufactured by the manufacturing method described above.

[0148] In the present invention, preferably, the specific surface area of ​​the hard carbon material is 6 to 10 m². 2 g -1 That is the case.

[0149] In the present invention, preferably, the hard carbon material has a sodium storage specific capacity greater than 250 mAh / g at a high rate of 20C.

[0150] In the present invention, preferably, the hard carbon material has a lithium storage specific capacity greater than 300 mAh / g at a high rate of 20C.

[0151] The present invention further provides the use of the hard carbon material described above in secondary batteries.

[0152] The present invention further provides a secondary battery comprising the hard carbon material described above.

[0153] In the present invention, preferably, the secondary battery is a lithium-ion battery or a sodium-ion battery.

[0154] Assuming that they conform to common sense in the field, any combination of the above preferred conditions can yield any of the preferred embodiments of the present invention.

[0155] All reagents and raw materials used in this invention can be obtained through commercial channels.

[0156] The positive and progressive effects of this invention are as follows:

[0157] The manufacturing method of the present invention achieves a more efficient dechlorination reaction by directly using a simple solid-phase method instead of dissolving the polymer material in an organic solvent, thereby promoting graphitization while avoiding the release of chlorine. Furthermore, since the template and pore-forming effects of the metal and salt contribute to improving the specific surface area of ​​the material, the manufactured hard carbon material has better electrochemical performance when used in lithium / sodium ion batteries, and in particular, it has a desirable specific capacity and 20C rate performance. [Brief explanation of the drawing]

[0158] [Figure 1] Figure 1 shows a high-resolution transmission electron microscope image of the hard carbon material produced in Example 1a. [Figure 2] Figure 2 shows a high-resolution transmission electron microscope image of the hard carbon material produced in Comparative Example 1a. [Figure 3]Part (a) of Figure 3 is an HRTEM image of the hard carbon material produced in Example 1b, and part (b) of Figure 3 is an FFT image of the hard carbon material produced in Example 1b. [Figure 4] Figure 4 is a scanning electron microscope image of the hard carbon material produced in Example 1c. [Modes for carrying out the invention]

[0159] The present invention will be further described below with reference to examples, but this does not limit the present invention to the scope of the examples below. For experimental methods in the examples below where specific conditions are not specified, general methods and conditions should be followed, or selected according to the product description.

[0160] The information on the raw materials used in the following Examples 1a to 8a and Comparative Example 1a is shown in Table 1.

[0161] [Table 1]

[0162] The raw materials used in Examples 1a to 8a and Comparative Example 1a were all obtained through normal commercial channels and no further processing was performed before use.

[0163] Example 1a (1) 1 g of PVC was dissolved in 30 mL of N-methylpyrrolidone (NMP) and stirred at room temperature for 10 minutes. After the PVC was completely dissolved in the NMP, 0.09 g of chlorobenzene was added and stirring was continued under heating conditions of 70°C. During this process, as the solvent evaporated, the solution gradually became viscous and formed a colloidal system. After stirring for 2 hours, the sol-gelation process was completed. The obtained clear sol was then placed on a magnetic hot stirrer at 150°C and stirring was continued until the solvent had completely evaporated and a dark gray dry gel was obtained. Next, the obtained dry gel was pulverized into a powder, washed with ethanol and water, and then dried in an oven for 12 hours to obtain a benzene ring-assisted PVC dehalogenation precursor.

[0164] (2) Subsequently, the benzene ring-assisted PVC dehalogenation precursor was pulverized into a powder and carbonized in a tubular furnace. At this time, it was heated to 800°C under a 300 sccm argon gas atmosphere. The heating rate was 5°C min. -1 The carbonization process was maintained for 120 minutes. After the carbonization reaction was complete, the material was allowed to cool naturally to room temperature to obtain the hard carbon material.

[0165] Example 2a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that the amount of chlorobenzene used was adjusted to 0.05 g.

[0166] Example 3a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that the amount of chlorobenzene used was adjusted to 0.12 g.

[0167] Example 4a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that the amount of chlorobenzene used was adjusted to 0.18 g.

[0168] Example 5a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that chlorobenzene was replaced with toluene.

[0169] Example 6a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that chlorobenzene was replaced with 1,2-dichlorobenzene.

[0170] Example 7a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that chlorobenzene was replaced with naphthalene.

[0171] Example 8a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that chlorobenzene was replaced with benzoic acid.

[0172] Comparative Example 1a Compared to Example 1a, the remaining operations and conditions were the same as in Example 1a, except that chlorobenzene was not added.

[0173] Examples of effects (1) Morphological characteristics assessment Figure 1 shows a high-resolution transmission electron microscope (HRTEM) image of the hard carbon material produced in Example 1a, and Figure 2 shows a high-resolution transmission electron microscope (HRTEM) image of the hard carbon material produced in Comparative Example 1a. As is clear from Figures 1 and 2, since the hard carbon material produced in Comparative Example 1a did not have a benzene ring structure introduced, micron-level clumps were formed, and a porous structure was not observed. Furthermore, no clear particle aggregation was observed on the surface of the clumps. Moreover, the interior had a typical hard carbon structure in which highly disordered turbostratic structures and curved carbon layer structures with short-range order were randomly intertwined. In contrast, in the hard carbon material produced in Example 1a, a pore structure and a more sparse surface could be clearly observed from Figure 1. Furthermore, the edges of the carbon crystal lattice were gradually formed locally, and the number of small-layer graphene-like nanocrystalline domains and micropores increased significantly. This indicates that the adsorption and deposition of benzene rings occurred mainly at the pore walls, and a large number of graphene nanocrystalline domains were generated inside the hard carbon material. This allows lithium ions to easily penetrate the bulk structure of the material, contributing to an increase in lithium ion storage capacity.

[0174] [Table 2]

[0175] In addition, the interlayer distance of the hard carbon material decreased from 0.433 nm in Comparative Example 1a to 0.401 nm in Example 1a and 0.380 nm in Example 4a. Although the interlayer distance decreased with the growth of graphene-like nanocrystalline domains, the interlayer distance of the hard carbon material was still larger than the average interlayer distance of graphite (0.335 nm), which was advantageous for ion insertion and movement. The presence and continuous growth of these ordered nanocrystalline domains not only filled the voids but also created a rich pore structure through folding, bending, and crosslinking of more carbon layers. Microporous structures and more slit pores were introduced into the overlapping, crosslinked, and twisted carbon layers. The micropores not only increased the plateau capacity by providing more void insertion sites but also provided pathways for lithium ions to enter the interior of the electrode material, enabling a reduction in the diffusion distance of lithium ions within the bulk.

[0176] (2) XRD Characterization XRD measurements revealed that the hard carbon material produced in Example 1a exhibited two similar broad diffraction peaks around 2θ ≈ 23° and 44°, corresponding to the Bragg reflects of the (001) and (100) crystal planes of graphite, respectively. These two broad peaks indicated that the carbon layer structure within the hard carbon material had low crystallinity and belonged to the characteristic peaks of amorphous carbon. Furthermore, as the amount of chlorobenzene additive increased, the (002) peak shifted to a higher diffraction angle. This indicated a reduction in the average interlayer distance between graphite layers. The interlayer distance d was calculated using Bragg's law. 002 The wavelength was reduced from 0.394 nm (Comparative Example 1a) to 0.363 nm (Example 1a) and 0.358 nm (Example 4a), which was consistent with the conditions observed by HRTEM.

[0177] (3) Raman spectroscopy, nitrogen adsorption / desorption characteristic evaluation test, FT-IR spectroscopy measurement Following general procedures in this field, the hard carbon materials produced in Example and Comparative Example 1a were subjected to Raman spectroscopy, nitrogen adsorption / desorption characteristic evaluation tests, and FT-IR spectroscopy measurements.

[0178] [Table 3]

[0179] Raman measurements were performed on the hard carbon materials produced in Example 1a, Example 4a, and Comparative Example 1a, and the results showed that all measured 1600 cm². -1 and 1350cm -1 The surrounding bands showed a wide frequency range. These two peaks are the G band (graphite band: sp) respectively. 2 E of the carbon ring 2g (Related to vibration modes) and D-band (disorder band: sp) 2 A of the carbon ring 1g It corresponded to the vibration mode. The ID / IG ratios for Comparative Example 1a, Example 1a, and Example 4a were 1.032, 1.024, and 0.951, respectively. This indicates that the defect content in the sample of Example 4a was significantly lower than that of Comparative Example 1a and Example 1a, and that the difference in the amount of benzene ring added had a clear modulating effect on the degree of disorder of the hard carbon material. In addition, in Example 4a, 2700 cm -1 A faint 2D peak appeared nearby, representing the deposition of small carbon layers with short- or medium-range order. The appearance of the 2D peak indicates that sufficient aromatic precursors were added during the manufacturing process, which decompose at high temperatures to form sp molecules containing benzene rings. 2 We demonstrated that by generating an intermediate and adsorbing it onto the pore wall, it could contribute to the growth of graphene-like nanodomains as a crystal nucleus when carbon atoms become graphitized carbon.

[0180] Evaluation of the nitrogen adsorption and desorption properties of the hard carbon material revealed that the specific surface area, average pore volume, and average pore diameter decreased as the amount of benzene rings added increased. As the amount of chlorobenzene added increased, the pore diameter clearly decreased, and the pore distribution shifted clearly towards finer pores. This indicated that a large number of voids within the original Comparative Example 1a were filled by a small number of deposited graphene-like nanodomains. Furthermore, the clear reduction in pore diameter distribution was attributed to the adsorption of benzene ring molecules onto the internal slit pore walls due to van der Waals forces between their electron cloud density and the π orbitals of the carbon plane. The adsorption of benzene ring molecules on the pore walls and the subsequent sealing of voids by the continuously deposited graphene-carbon layers reduced the pore diameter. Additionally, the small number of graphene-like nanodomains formed on the slit pore walls prevented gas evaporation during the thermal decomposition process, creating closed voids within the carbon material. The pore diameter distribution range in Example 4a was clearly smaller than that of Example 1a. In Example 4a, the pore size was reduced to 0.96 nm or less due to the excessive filling of nanodomains (Li in carbonate electrolytes). + The Stokes radius is approximately 0.48 nm, and the solvated Li is present in the micropores. + The insertion of Li was prevented, + Intercalation of dissolved Li decreases. + The effective transport of ions was inhibited.

[0181] Infrared measurement results indicate that PVC has a range of 600-640 cm -1 The C-Cl stretching vibration peak between 1180 and 1350 cm -1 Nearby H-CCl deformation vibration peaks and 1433 cm -1 Nearby -CH2 deformation vibration peak and ~2906cm -1 and 2967cm -1 Clear characteristic peaks of chlorinated hydrocarbons were found in the vicinity of HCH and the CH stretching vibration peak in Cl-C-. However, after high-temperature carbonization, all characteristic peaks of chlorinated hydrocarbons disappeared, and consequently, ~1670 cm -1A bending vibration peak of C=C appeared in the vicinity. This indicates that all chlorine atoms were removed from the molecular chain of Comparative Example 1a, and that a conjugated carbon-carbon double bond was present. With the introduction of the benzene structure, in Example 1a, ~1350 cm⁻¹ -1 A shear vibration peak of RC=CH- was observed nearby. This is because, after the introduction of the benzene ring, electron rearrangement resulting from the interaction between the π orbitals in the PVC-derived carbon layer and the electronic structure in the benzene structure occurs during the carbonization process. 2 - This demonstrated an even more favorable effect on maintaining the C structure. In other words, the addition of aromatic additives contributed to the generation of more ordered, smaller layers of graphene-like material within the polyvinyl chloride-derived hard carbon.

[0182] (4) Conductivity measurement The hard carbon materials produced in Examples 1a to 4a and Comparative Example 1a were compressed into sheets at room temperature of 25°C, and their conductivity was measured. A certain amount of PVP was added as a binder when preparing the sheet-like samples by compression. Subsequently, the resistance of the compressed sheet samples was measured using an ohmmeter, and the conductivity was as shown in Table 4. The calculation formula is as follows.

[0183] R = ρ(L / πr) 2 ) σ = 1 / ρ In the formula, the resistance R (BPC sheet resistance of the compression sheet, unit: Ω) was measured using an ohmmeter, and L (thickness of the compression sheet, unit: m) was measured using calipers. Also, r (radius of the carbon sheet, unit: m) was a fixed value of 3 × 10⁻⁶. -3 Let's call it m.

[0184] [Table 4]

[0185] (5) Electrochemical performance test Button batteries were fabricated using PVC-derived highly conductive carbon-based samples, and their electrochemical performance was investigated. 400 mg of the hard carbon material prepared in Examples 1a-8a and Comparative Example 1a was weighed along with 50 mg of conductive carbon black Super P and 50 mg of PVDF (mass ratio 8:1:1). The mixture was pulverized and uniformly mixed, then added to NMP solvent. The mixture was then homogenized to obtain a polyvinyl chloride-based highly conductive carbon paste. Next, the paste was applied to copper foil and dried overnight in a vacuum oven at 85°C. The obtained electrode copper foil was then cut into circular sheet-shaped battery plates with a diameter of 12 mm. The average mass load was approximately 2 mg cm². -2 That was the case.

[0186] Electrochemical measurements of the sample were performed by assembling a CR-2016 button cell in a glove box filled with argon gas. The electrolyte used was LB046. The specific composition was 1 mol L. -1 A 5 wt% FEC additive was added to a LiClO4 ethylene carbonate EC / DEC (1:1 v / v) mixed solution. A single layer of polypropylene (PP) was used as the separator, and lithium metal foil was used as the negative electrode. Charge and discharge tests were performed using a LAND CT2001A battery tester within a potential range of 0.001 to 3.0V.

[0187] Electrodes were fabricated using hard carbon material, and lithium storage performance was measured within a half-cell. Table 5 shows the current density at 50 mA g. -1 This shows the initial charge-discharge data for the hard carbon material anode under these conditions.

[0188] [Table 5]

[0189] [Table 6]

[0190] As is evident from the data in Tables 5 and 6, Examples 1a to 8a showed higher reversible ratio capacity and better initial Coulombic efficiency compared to Comparative Example 1a. The higher reversible ratio capacity may be due to the presence of additional small layers of graphene-like nanodomains within their structures. Furthermore, the better initial Coulombic efficiency may be due to the suppression of side reactions with the electrolyte by reducing their specific surface area and significantly reducing defects. As is evident from the characterization of the physical structure described above, the introduction of a benzene ring structure caused a reconstruction of the carbon layer in the microstructure of the hard carbon material, resulting in the growth of more ordered, small-layer graphene-like carbon layer structures. These ordered graphene microcrystalline carbon domains provide an electron transport network, and the voids formed by the intersecting curved carbon layers and the ordered carbon layers also provide additional sites for lithium ion insertion / desorption and lithium ion storage, and these interactions resulted in increased capacity.

[0191] The raw materials used in the following Examples 1b to 6b and Comparative Examples 1b to 6b are shown in Table 7.

[0192] [Table 7]

[0193] Example 1b (1) Pre-dehalogenation 1 g of PVC and 0.1 g of polypropylene were heated and melted in a heating furnace (under an argon gas atmosphere). The heating temperature was 120°C and the heating time was 2 hours. After cooling, substance A was obtained.

[0194] Material A was placed in a quartz crucible, and the crucible was placed inside a tubular furnace for pre-dehalogenation. It was heated to 360°C under a 300 sccm argon gas flow and maintained at that temperature for 120 minutes. The heating rate was 5°C min. -1The mixture was allowed to cool naturally to room temperature, and the resulting mass was then pulverized into a powder. The sample was then washed with a mixture of deionized water and anhydrous ethanol in a volume ratio of 3:1, and dried to obtain a pre-dehalogenated sample.

[0195] (2) Carbonization After weighing an appropriate amount of pre-dehalogenated sample powder and placing it in a quartz glass test tube, weigh out NaCl solid and cover the pre-dehalogenated sample powder directly with it, and then place it under vacuum conditions (vacuum conditions: 10°C). -2 The upper end of a quartz tube was heated and melted with an oxyhydrogen flame at a temperature of less than mbar and then vacuum-sealed. The mass ratio of NaCl to the pre-dehalogenated sample was 2:1. The quartz tube was then placed in a muffle furnace and carbonized at 820°C for 10 hours. The heating rate was 5°C / min. After the carbonization reaction was complete, the tube was cooled to room temperature and removed. The quartz glass tube was cut, and the obtained material was washed with a mixed solution of water and ethanol (volume ratio 1:3) to remove the NaCl melting aid. After drying, the obtained material was pulverized into a powder and collected to obtain a polyvinyl chloride-derived hard carbon material.

[0196] Example 2b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that the mass ratio of NaCl to the pre-dehalogenated sample in step (2) was adjusted to 3:1.

[0197] Example 3b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that the carbonization temperature in step (2) was adjusted to 900°C.

[0198] Example 4b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that NaCl in step (2) was replaced with sodium bromide and the carbonization temperature was adjusted to 800°C.

[0199] Example 5b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that NaCl in step (2) was replaced with potassium chloride.

[0200] Example 6b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that polypropylene in step (1) was replaced with polyethylene.

[0201] Comparative example 1b We used commercially available hard carbon BHC-550 (purchased from Chengdu BSG Technology Co. Ltd.).

[0202] Comparative Example 2b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that NaCl was not added in step (2).

[0203] Comparative Example 3b (Carbonizing PVC as is) An appropriate amount of PVC powder was weighed and placed into a quartz tube, which was then sealed after vacuum evacuation. The quartz tube was then placed in a muffle furnace and carbonized at 820°C for 10 hours. The heating rate was set to 5°C / min. After the carbonization reaction was complete, the tube was allowed to cool to room temperature and removed. The quartz glass tube was then cut, and the obtained material was washed with a mixture of deionized water and anhydrous ethanol in a volume ratio of 3:1. After drying, the resulting material was pulverized into a powder and collected to obtain hard carbon material.

[0204] Comparative example 4b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that the mass ratio of NaCl to the pre-dehalogenated sample in step (2) was adjusted to 5:1.

[0205] Comparative Example 5b Compared to Example 1b, the remaining operations and conditions were the same as in Example 1b, except that the carbonization temperature in step (2) was adjusted to 700°C.

[0206] Comparative Example 6b Compared to Example 1b, all other operations and conditions were the same as in Example 1b, except that polypropylene was not added.

[0207] Examples of effects (1) Morphological characteristics assessment Morphological characteristics were evaluated for the manufactured polyvinyl chloride-derived hard carbon material and the pre-dehalogenated sample. Observation by SEM electron microscopy revealed that the pre-dehalogenated sample had a sparse surface and consisted of coarse, randomly aggregated parts without any special shape. However, after high-temperature carbonization with NaCl assistance, it formed solid hard carbon particles with clearly defined edges. Furthermore, HRTEM and FFT images (Figure 3) showed that the manufactured hard carbon material had a composite hard carbon structure with a continuous, few-layer (n<5) graphene-carbon layer on the outside and a disordered turbostratic structure inside.

[0208] (2) XRD Characterization XRD measurements revealed that the hard carbon materials produced in Examples 1b, 3b, and 5b all exhibited two broad characteristic peaks around 25° and 42°. These correspond to diffraction at the (002) and (100) crystal planes in a typical disordered amorphous carbon structure, demonstrating that the hard carbon materials are typical disordered hard carbon. Furthermore, as the carbonization temperature increased, the peak corresponding to the (002) crystal plane around 25° became even broader, its position shifted to the left, and its peak intensity gradually weakened. This indicates that the degree of structural disorder increased, and the interlayer distance of the curved carbon layers in the plane expanded. Bragg's law calculated the interlayer distance d 002The interlayer distance expanded from 0.351 nm in Comparative Example 5b to 0.354 nm in Example 1b, and further to 0.361 nm in Example 3b. In contrast, the interlayer distance of Comparative Example 1b was only 0.347 nm. The expansion of the interlayer distance also demonstrated that, during the high-temperature carbonization process under NaCl assistance, the generated HCl was not rapidly released, and the HCl gas trapped inside the molten NaCl salt continued to impact the internal structure of the hard carbon material during the carbonization process, promoting the generation of more dense disordered structures within the material and providing the driving force for the expansion of the interlayer distance.

[0209] Furthermore, from the XRD measurement results of Examples 1b-2b and Comparative Example 4b, it was found that as the amount of NaCl added increases, the hard carbon material exhibits a stronger (002) characteristic peak intensity around 25° and a narrower peak width, but the peak position does not shift. As is clear from the measurement results in Table 8, for Examples 1b-2b and Comparative Example 4b, with increasing amounts of NaCl added, D / I G The value decreased and then increased, with Comparative Example 4b showing the highest I D / I G The values ​​shown indicate that the sealing effect improves as the amount of NaCl, the sealing layer agent, increases, and the difficulty in releasing HCl gas generated during the thermal decomposition process of the pre-dehalogenated sample increases, resulting in a stronger destructive effect on the internal structure. Therefore, Comparative Example 4b showed a higher degree of disorder in the internal, disordered turbostratic structure.

[0210] (3) Raman spectroscopy, nitrogen adsorption / desorption characteristic evaluation test, FT-IR spectroscopy measurement Following general procedures in this field, Raman spectroscopy, nitrogen adsorption / desorption characteristic evaluation tests, and FT-IR spectroscopy measurements were performed on the hard carbon materials produced in the Examples and Comparative Examples, as well as the pre-dehalogenated sample produced in Example 1b.

[0211] Raman spectroscopy revealed that the ID / IG peak intensity ratios for the pre-dehalogenated sample prepared in Example 1b and the hard carbon materials prepared in Comparative Examples 1b, 5b, Example 1b, and 3b were 1.067, 1.048, 0.910, 0.965, and 0.991, respectively. The degree of defects in the material can be determined from the intensity ratio of the D peak to the G peak (ID / IG), with a smaller ratio indicating fewer defects. This indicates that the degree of defects is significantly reduced compared to commercially available hard carbon BHC550 with the introduction of the NaCl melting aid. Furthermore, as the carbonization temperature increases, the destructive effect of the HCl gas flow generated during the carbonization process of the pre-dehalogenated sample on the structure increases. Therefore, at appropriate temperatures, the degree of defects in the hard carbon material becomes higher, and the internal structure becomes even more disordered. This was consistent with the XRD results.

[0212] [Table 8]

[0213] Furthermore, the HCl gas stream generated during the carbonization process of the pre-dehalogenated samples also had a significant pore-forming effect on the interior of the hard carbon material. As is clear from the measurement results in Table 8, the specific surface area and pore size of the hard carbon material increased as the carbonization temperature rose. These results indicate that under vacuum conditions, as the temperature rises, the rate of gas release generated in the dechlorination reaction increases, and the impact effect of the gas on the internal structure intensifies. As a result, the hard carbon material acquires more microstructures, increasing the degree of disorder and developing void structures. This is advantageous when using hard carbon material as an energy storage material, as it provides more active sites for ion storage and increases the specific capacity of the material.

[0214] From the FT-IR spectrum, the PVC sample has a range of 600-640 cm⁻¹. -1 C-Cl stretching vibration peak between 1180 and 1350 cm -1 The H-CCl bending vibration peaks between 2906 and 2967 cm. -1A series of characteristic peaks of chlorinated hydrocarbons, such as the Cl-C bending vibration peak, were found to exist between these points. However, after prior dehalogenation, the peaks changed to 600-640 cm⁻¹. -1 Nearby C-Cl peaks and 2906-2967 cm -1 The nearby Cl-C peak has clearly weakened. Also, 1180-1350cm -1 The H-CCl bending vibration peak during this period changed to the -CH2 bending vibration peak. Furthermore, a new ~1670cm² range was introduced. -1 The appearance of C=C bending oscillation peaks in the vicinity was observed. These changes in peak positions all indicate that, through a pre-dehalogenation reaction at low temperatures, chlorine is partially removed, resulting in sp(C=C) content. 2 This demonstrated that the intermediate was present in the molecular chain of the pre-dehalogenated sample. Furthermore, in the hard carbon material of Example 1b, obtained after subsequent high-temperature carbonization, all characteristic peaks of chlorinated hydrocarbons and the C=C peak disappeared. This indicated the completion of the dehalogenation reaction. Moreover, due to the growth and rearrangement of the carbon layer, it became difficult to maintain the olefin intermediate containing C=C under the impact of the HCl gas stream, resulting in the formation of a disordered turbostratic structure. In addition, Raman measurements of PVC, the pre-dehalogenated sample, and the hard carbon material showed that after pre-dehalogenation, some sp(s) were present in the pre-dehalogenated sample compared to PVC. 2 It was found that a hybridized carbon intermediate was formed, resulting in the appearance of D and G peaks. Calculations showed that the intensity ratio of the D and G peaks in the pre-dehalogenated sample precursor was 1.067, which was higher than that of the hard carbon material (0.965). This indicates that the subsequent carbonization process, through the removal of Cl and rearrangement of the carbon layer, significantly reduced defects in the hard carbon. The removal of chlorine-related characteristic peaks in the hard carbon material and the optimization of the surface carbon defect level further demonstrated the formation of a unique structure in which the outer layer is coated with a graphene carbon layer and the interior consists of turbostratic and amorphous carbon.

[0215] (4) The carbon yield of polyvinyl chloride-derived hard carbon materials produced by the two-stage process and coated with a small layer of graphene reached 26-33%. This was significantly higher than the carbon yield of other PVC-derived carbon materials that have already been reported. Therefore, from an environmental and economic standpoint, converting polyvinyl chloride waste plastics into high-value carbon-based materials using the two-stage pyrolysis method promotes resource recovery and offers the potential for sustainable development.

[0216] (5) Electrochemical performance testing of lithium-ion batteries CR-2016 button batteries were assembled, and electrochemical measurements were performed on the prepared samples. For the working electrode plates, a mixed paste was applied to a copper foil current collector, dried overnight at 85°C in a vacuum oven, and then cut into 1cm x 1cm circular plates. The paste consisted of an active substance (manufactured hard carbon material), superconducting carbon black (Super P), and a PVDF binder dispersed in NMP in an 8:1:1 weight ratio. The button batteries were fabricated in a glove box filled with argon gas. A lithium metal foil was used as the negative electrode, and a single layer of polypropylene (PP) was used as the separator. 1 mol L of LB046 electrolyte was used. -1 LiClO4 was dissolved in an EC / DEC mixed solution (volume ratio 1:1), and 5 wt% fluoroethylene carbonate (FEC) was added as an additive. Charge / discharge tests were performed using the LAND CT2001A battery test system. The temperature was set to 20°C. The voltage range for rate performance and long-term cycle performance tests was 0.001~2.5V vs. Li / Li + (1C = 250mAh g) -1 )

[0217] [Table 9]

[0218] Based on the results in Table 9, by comparing Examples 1b to 2b and Comparative Example 4b, it was found that when the mass ratio of NaCl to the pre-dehalogenated sample was not in the range of (1.2 to 4.5):1, the specific capacity and initial Coulombic efficiency of the produced hard carbon material decreased. Also, by comparing Example 1b, Example 3b, and Comparative Example 5b, it was found that when the carbonization temperature was lower than the melting point of the salt, the initial reversible specific capacity and initial Coulombic efficiency of the produced hard carbon material decreased.

[0219] The procedure for the rate test was 0.5C, 1C, 2C, 5C, 10C, 20C, 30C, 40C, 50C, 60C (1C = 250 mAh g -1 ), and after completing the rate test once, the current was returned to 0.5C again. The negative electrode of the hard carbon material produced in Example 1b had reversible capacities of 396.0 mAh g -1 , 362.7 mAh g -1 , 335.3 mAh g -1 , 297.1 mAh g -1 , 267.8 mAh g -1 , 229.9 mAh g -1 , 208.5 mAh g -1 , 191.5 mAh g -1 , 176.3 mAh g -1 , and 163.4 mAh g -1 at 0.5C, 1C, 2C, 5C, 10C, 20C, 30C, 40C, 50C, 60C currents, respectively. When the current was rapidly returned to 0.5C, the reversible capacity of the hard carbon material produced in Example 1b quickly recovered to 392.1 mAh g -1 and had good cycle reversibility. The ratio of the reversible capacity of the hard carbon material produced in Example 1b at 5C to that at 0.1C was 75%, which was much higher than 60%. This indicated that the hard carbon material produced in Example 1b had excellent rate performance even when evaluated at an industrial level. In contrast, in Comparative Example 1b, Comparative Example 2b, Comparative Example 3b, Comparative Example 5b, and Example 3b, the reversible capacities corresponding to 60C were 30.7 mAh g -1 , 31.0 mAh g -1, 31.1mAh g -1 , 33.8mAh g -1 and 34.5mAh g -1 That was the case.

[0220] By comparing the initial charge-discharge behavior of Example 1b and Comparative Examples 2b-3b, it was found that even when using the same precursor carbon source, the introduction of NaCl molten salt as a graphene template and encapsulant is essential for the formation of the unique structure of the hard carbon material. In all cases, the PVC-derived pyrolysis carbon had its heteroatom Cl removed by high-temperature treatment, reducing the degree of defects in the carbon material and resulting in highly conductive carbon. Therefore, both Example 1b and Comparative Examples 2b-3b clearly exhibited superior initial Coulombic efficiency compared to the commercially available hard carbon BHC550 used in Comparative Example 1b. However, in Comparative Examples 2b-3b, the rearrangement process of the surface carbon layer assisted by NaCl was absent, limiting the solid diffusion process within the material, resulting in a limited rate capacity.

[0221] [Table 10]

[0222] As is clear from the results in Table 10, the hard carbon material produced in Example 1b exhibited the highest capacity retention rate regardless of the current density. The hard carbon material electrode possessed optimal electrochemical performance due to its unique structure. Specifically, the thin graphene carbon layer promoted rapid ion / electron transport, significantly improving reaction kinetics. Furthermore, the disordered turbostratic structure contributed to maintaining the structure of the hard carbon material electrode during the electrochemical cycle process, reducing electrode breakage. The conductivity of the hard carbon material was improved by the graphenization process assisted by NaCl. Moreover, the development of the void structure became advantageous for repeated insertion / deinsertion of lithium ions. Therefore, from an environmental and economic standpoint, producing polyvinyl chloride-derived hard carbon coated with a thin graphene layer by stepwise pyrolysis with NaCl assistance can be said to realize the development of a high-value and functional carbon-based material, providing a new concept for the upcycling of polyvinyl chloride waste plastics.

[0223] (6) Electrochemical performance test of potassium-ion batteries CR-2016 button batteries were assembled, and electrochemical measurements were performed on the prepared samples. For the working electrode plates, a mixed paste was applied to a copper foil current collector, dried overnight at 85°C in a vacuum oven, and then cut into 1cm x 1cm circular plates. The paste consisted of an active substance (manufactured hard carbon material), superconducting carbon black (Super P), and a PVDF binder dispersed in NMP in an 8:1:1 weight ratio. The button batteries were fabricated in a glove box filled with argon gas. Potassium metal foil was used as the negative electrode, and a single layer of polypropylene (PP) was used as the separator. 1 mol L of LB046 electrolyte was used. -1KPF6 was dissolved in an EC / DEC mixed solution (volume ratio 1:1), and 5 wt% fluoroethylene carbonate (FEC) was added as an additive. Charge / discharge tests were performed using a LAND CT2001A battery test system. The temperature was set to 20°C. The voltage range for rate performance and long-term cycle performance tests was 0.001~2.5V vs. K / K + (1C = 250mAh g) -1 )

[0224] K / K + After assembling the half-cells and examining the potassium ion storage performance of the hard carbon material manufactured in Example 1b, the results showed that during the initial charge / discharge at 0.5C, the storage capacity was 312.2 / 478.6 mAh g. -1 The capacity was shown, and the initial Coulomb efficiency was 65.2%. In contrast, the commercially available BHC550 in Comparative Example 1b showed 265.8 / 373.2mAh g -1 The capacity was shown, and the initial Coulomb efficiency was 71.2%. On the other hand, in Example 1b, the reversible capacity at 0.5C, 1C, 2C, 5C, and 10C was 333.4mAh g, respectively. -1 , 294.1mAh g -1 , 256.4mAh g -1 , 205.3mAh g -1 and 168.2mAh g -1 Furthermore, even at a high current density of 20C, the specific capacity of Example 1b was 128.7mAh g. -1 This was maintained, and 76.3% of the reversible capacitance at a current density of 10C was maintained. In contrast, the BHC550 and graphite electrode of Comparative Example 1b had a specific capacitance of 67.2 mA hg at 20C. -1 Furthermore, when the current density was rapidly returned to 0.5C, the specific capacity of BHC550 in Example 1b and Comparative Example 1b was 297.4mAh g, respectively. -1 and 203.3mAh g -1had recovered. The excellent high-rate performance of potassium ions in Example 1b may be due to the promotion of the storage and transport of potassium ions in the potassium insertion / desorption process by the few-layer graphene layers in the hard carbon material. The hard carbon material maintained a high reversible capacity of 234.5 mAh g -1 when cycled at 1C for 100 cycles, and the capacity retention rate after 300 cycles was 74.27%. Also, in Example 1b, the capacity retention rate after 800 cycles at 5C was 68%, and the average capacity degradation rate per cycle was 0.04%. Therefore, when the hard carbon derived from polyvinyl chloride coated with ordered graphene under the assistance of NaCl is manufactured as the negative electrode of a potassium ion battery, it is possible to have high capacity, high-rate performance, and good cycle stability.

[0225] The information on the raw materials used in the following Examples 1c to 8c and Comparative Example 1c is as shown in Table 11.

[0226]

Table 11

[0227] Example 1c (1) After mixing 1 g of PVC and 0.05 g of polyethylene, it was heated and melted in a tubular furnace (under an argon gas atmosphere). The heating temperature was 120°C and the heating time was 2 h, and Substance A was obtained after cooling.

[0228] (2) Substance A and metallic sodium were uniformly mixed and put into a crucible so that the molar ratio of chlorine atoms to metallic sodium in the raw material PVC was 1:1.3. The crucible was put into the tubular furnace and heated to 250°C at a heating rate of 3°C / min in a high-purity argon gas atmosphere. Then, after maintaining for 3 h and cooling to room temperature, a dehalogenated sample was obtained.

[0229] (3) The dehalogenated sample was washed three times with a mixture of deionized water and anhydrous ethanol in a volume ratio of 3:1, and dried to obtain a hard carbon precursor. Next, the hard carbon precursor was heated to 800°C at a rate of 5°C / min in a tubular furnace in high-purity argon gas and maintained for 4 hours to carbonize, and then cooled to obtain a hard carbon anode material.

[0230] Example 2c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that the polyvinyl chloride powder was replaced with PVDC powder (SARAN 516, extruded type, from The Dow Chemical Company).

[0231] Example 3c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that metallic sodium was replaced with metallic potassium.

[0232] Example 4c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that metallic sodium was replaced with metallic potassium, and the molar ratio of chlorine atoms to metallic potassium in the PVC was adjusted to 1:1.1.

[0233] Example 5c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that metallic sodium was replaced with metallic magnesium and the molar ratio of chlorine atoms to metallic magnesium in the PVC was adjusted to 1:0.55.

[0234] Example 6c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that metallic sodium was replaced with metallic calcium and the molar ratio of chlorine atoms to metallic calcium in the PVC was adjusted to 1:0.55.

[0235] Example 7c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that the carbonization temperature in step (3) was adjusted to 900°C.

[0236] Example 8c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that polyethylene was replaced with polypropylene.

[0237] Comparative example 1c Compared to Example 1c, all other parameters and conditions were the same as in Example 1c, except that metallic sodium was not added in step (1).

[0238] Examples of effects (1) SEM and specific surface area measurement Figure 4 is a scanning electron microscope image of the hard carbon material produced in Example 1c. The specific surface area of ​​the manufactured hard carbon material was measured using Anton Paar's NOVATouch specific surface area and pore size analyzer. The measurement results are shown in Table 12.

[0239] (2) Electrochemical performance test Fabrication of Negative Electrode Plates: Half-cell measurements were performed on the hard carbon materials manufactured in Examples 1c to 8c and Comparative Example 1c. The measurement method was as follows: Hard carbon material, superconducting carbon black (Super P), and PVDF were mixed in a mass ratio of 8:1:1, homogenized, and then coated onto a copper foil current collector and dried overnight in a vacuum oven at 90°C. After that, the obtained electrode plates were cut into circular sheet-shaped battery electrode plates with a diameter of 12 mm. The average mass load was approximately 2 mg cm². -2 That was the case.

[0240] The assembly of button batteries was all carried out inside a glove box filled with argon gas. For lithium-ion batteries, lithium metal foil was used as the counter electrode, and a single layer of polypropylene was used as the separator. Also, an electrolyte solution was used in which 10 wt.% of fluoroethylene carbonate (FEC) was added as an additive to a mixed solution of 1M LiClO4 in ethylene carbonate / diethyl carbonate (EC / DEC, volume ratio 1:1). wt.% represents the mass percentage of FEC in the electrolyte solution. The charge-discharge test was carried out within a potential range of 0.001 - 3.0V using a LAND CT2001A battery tester.

[0241] For sodium-ion batteries, sodium metal foil was used as the counter electrode, a single layer of glass fiber was used as the separator, and a nickel foam circular sheet was additionally added. The electrolyte solution was a 1M NaPF6 solution in diethylene glycol dimethyl ether. After completion of the assembly, it was left standing for 8h for aging. Then, a constant current charge / discharge test was carried out using a LAND CT2001A battery test system. The voltage range was 0.001 - 3.0V vs. Na / Na + was used.

[0242] The measurement results were as shown in Table 12.

[0243]

Table 12

[0244] As is clear from the above experimental results, the hard carbon negative electrode material manufactured by the present invention has excellent electrochemical performance, and in particular, it is excellent in specific capacity and rate performance.

[0245] In Comparative Example 1c, since there was a lack of metal catalytic action during the manufacturing process, the efficiency of the dehalogenation reaction at the same temperature decreased, which was disadvantageous for forming highly conductive carbon. Also, due to the lack of the templating action of the metal and the salt, the specific surface area of the manufactured hard carbon material was small and the specific capacity decreased.

[0246] While specific embodiments of the present invention have been described above, these are merely illustrative examples, and those skilled in the art should understand that the scope of protection of the present invention is limited by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications shall all be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing hard carbon material, (1) A step of mixing a solution containing PVC and an aromatic compound under heating conditions until the solvent is completely evaporated to obtain a dry gel, (2) A step of obtaining a PVC dehalogenated precursor by crushing, washing and drying the dried gel, (3) The step of carbonizing the PVC dehalogenation precursor to obtain the hard carbon material, A method characterized in that the mass ratio of the aromatic compound to the PVC is 2 to 25%, the carbonization temperature is 700 to 1200°C, and the carbonization time is 1 to 4 hours.

2. The viscosity number K value of the aforementioned PVC is 50 to 80. The method for producing a hard carbon material according to claim 1, characterized in that the aromatic compound is a compound containing at least one benzene ring, and preferably an aromatic hydrocarbon and / or an aromatic hydrocarbon derivative.

3. The aforementioned aromatic hydrocarbons are monocyclic aromatic hydrocarbons and / or polycyclic aromatic hydrocarbons. Preferably, the monocyclic aromatic hydrocarbon is benzene or toluene. Preferably, the polycyclic aromatic hydrocarbon is a non-condensed ring aromatic hydrocarbon and / or a condensed ring aromatic hydrocarbon, such as biphenyl or naphthalene. and / or the aromatic hydrocarbon derivative is an aromatic acid and / or a halogenated aromatic hydrocarbon, Preferably, the aromatic acid is benzoic acid. Preferably, the halogen in the halogenated aromatic hydrocarbon is one or more of F, Cl, Br, and I. Preferably, the number of halogen atoms in the halogenated aromatic hydrocarbon is at least 1. Preferably, the halogenated aromatic hydrocarbon is a side-chain halogenated aromatic hydrocarbon and / or an aromatic ring halogenated aromatic hydrocarbon, and the aromatic ring halogenated aromatic hydrocarbon is, for example, chlorobenzene or 1,2-dichlorobenzene, characterized in that the method for producing a hard carbon material according to claim 2.

4. The aforementioned manufacturing method is (1) The mass ratio of the aromatic compound to the PVC is 7 to 15%. (2) The solvent in the solution is a solvent capable of dissolving PVC, for example, NMP. (3) The ratio of the mass of the PVC to the volume of the solvent in the solution is 1:(20-40) g / mL. A method for producing a hard carbon material according to claim 1, characterized in that one or more of the following conditions are met.

5. The aforementioned manufacturing method is (1) In step (1), the method for producing a solution containing the PVC and aromatic compound includes a process of stirring and mixing the PVC and solvent at room temperature until the PVC is completely dissolved, and then adding the aromatic compound. (2) In step (1), the temperature of the mixture is 140 to 180°C. (3) Step (1) includes, as the mixing process, first stirring the solution containing the PVC and aromatic compound at 60 to 90°C for 1 to 3 hours to obtain a sol, and then stirring the sol at 140 to 180°C until the solvent is completely evaporated to obtain a dry gel. A method for producing a hard carbon material according to claim 1, characterized in that one or more of the following conditions are met.

6. In step (3), the carbonization temperature is 700 to 900°C. The method for producing a hard carbon material according to claim 1, characterized in that the carbonization time is 1 to 3 hours.

7. A hard carbon material characterized by being manufactured according to the method for manufacturing a hard carbon material described in any one of claims 1 to 6.

8. The aforementioned hard carbon material is (1) The hard carbon material has a small graphene-like carbon layer structure inside it. (2) The graphite interlayer distance of the hard carbon material is 0.340 to 0.385 nm. (3) The pore size distribution range of the hard carbon material is 0.1 to 6 nm. (4) The specific surface area of ​​the hard carbon material is 1 to 5 m² ２ / g (5) The hard carbon material I Ｄ / I Ｇ The value is between 0.948 and 1.

05. (6) The conductivity of the hard carbon material is 1.14 to 5 S m －１ Being (7) The hard carbon material has a current density of 50 mA g －１ The reversible ratio capacity at that time is 355-600 mAh g －１ Being (8) The hard carbon material has a current density of 50 mA g －１ The initial Coulomb efficiency at that time is 70-85%. (9) The hard carbon material has a reversible specific capacity of 440 to 540 mAh g when the current density is 0.5 A g －１ , －１ and (10) The hard carbon material has a current density of 0.5 A g －１ The capacity retention rate after 300 cycles must be 99% or higher. (11) The hard carbon material has a current density of 1.5 A g －１ The reversible ratio capacity at that time is 120-210 mAh g －１ Being (12) The hard carbon material has a current density of 1.5 A g －１ The capacity retention rate after 1800 cycles must be 99% or higher. The hard carbon material according to claim 7, characterized in that it satisfies one or more of the following conditions.

9. Use of the hard carbon material in a battery according to claim 7 or 8.

10. A battery characterized by comprising the hard carbon material described in claim 7 or 8.

11. A method for producing a hard carbon material derived from polyvinyl chloride, (1) Heat and melt PVC powder and thermoplastic resin, obtain substance A after cooling, then perform a pre-dehalogenation reaction on substance A under inert gas shielding to obtain a pre-dehalogenated sample, wherein the thermoplastic resin is polypropylene and / or polyethylene, the mass ratio of the thermoplastic resin to the PVC powder is 5 to 50%, the temperature of the pre-dehalogenation reaction is 250 to 500°C, and the duration of the pre-dehalogenation reaction is 1 to 5 hours. (2) The pre-dehalogenated sample is covered with an inorganic halide salt in a reaction tube, the reaction tube is evacuated and sealed, and then carbonized, washed and dried to obtain the polyvinyl chloride-derived hard carbon material, wherein the mass ratio of the inorganic halide salt to the pre-dehalogenated sample is (1.2 to 4.5):1, the carbonization temperature is above the melting point of the inorganic halide salt, and the carbonization time is 5 to 20 hours. A method characterized by including the following.

12. Step (1) is, (1) The heating and melting temperature is 100 to 140°C. (2) The heating and melting time is 1 to 4 hours. (3) The temperature of the pre-dehalogenation reaction is 300 to 400°C. (4) The duration of the pre-dehalogenation reaction is 1 to 3 hours. A method for producing a polyvinyl chloride-derived hard carbon material according to claim 11, characterized in that one or more of the following conditions are met.

13. The aforementioned manufacturing method is (1) The viscosity number K value of the PVC powder is 50 to 80. (2) The melt flow index of the polypropylene is 10 to 40 g / 10 min. (3) The melt flow index of the polyethylene is 10 to 40 g / 10 min. (4) The mass ratio of the thermoplastic resin to the PVC powder is 5 to 20%. A method for producing a polyvinyl chloride-derived hard carbon material according to claim 11, characterized in that one or more of the following conditions are met.

14. The inorganic halide salt is, (1) The melting point of the inorganic halide salt is 700°C or higher. (2) The cation of the inorganic halide salt contains one or more of alkali metals, alkaline earth metals, and transition metals, Preferably, the alkali metal includes Na and / or K. Preferably, the alkaline earth metal includes one or more of Mg, Ca, Sr, and Ba. Preferably, the transition metal includes one or more of Fe, Co, Ni, Cu, and Zn. (3) The anion of the inorganic halide salt contains one or more of Cl ions, Br ions, and I ions, preferably Cl ions or Br ions. (4) The inorganic halide salt is one or more of NaCl, KCl, and NaBr. (5) The mass ratio of the inorganic halide salt to the pre-dehalogenated sample is (1.5 to 3.5):

1. A method for producing a polyvinyl chloride-derived hard carbon material according to claim 11, characterized in that one or more of the following conditions are met.

15. In step (2), preferably, the carbonization temperature is 10 to 200°C higher than the melting point of the inorganic halide salt. When the inorganic salt is NaCl, the carbonization temperature is preferably 810 to 1000°C. When the inorganic salt is NaBr, the carbonization temperature is preferably 780 to 900°C. When the inorganic salt is KCl, preferably the carbonization temperature is 800 to 1000°C. The method for producing a polyvinyl chloride-derived hard carbon material according to claim 11, characterized in that the carbonization time is 5 to 15 hours.

16. A polyvinyl chloride-derived hard carbon material characterized by being manufactured according to the method for manufacturing a polyvinyl chloride-derived hard carbon material described in any one of claims 11 to 15.

17. The polyvinyl chloride-derived hard carbon material according to claim 16, characterized in that the exterior of the polyvinyl chloride-derived hard carbon material is covered with a continuous, small layer of graphene carbon.

18. The aforementioned polyvinyl chloride-derived hard carbon material is (1) The graphite interlayer distance of the polyvinyl chloride-derived hard carbon material is 0.352 to 0.40 nm. (2) The pore size distribution range of the polyvinyl chloride-derived hard carbon material is 7.5 to 15 nm. (3) The specific surface area of ​​the polyvinyl chloride-derived hard carbon material is 4.8 to 15 m². ２ / g (4) The polyvinyl chloride-derived hard carbon material I Ｄ / I Ｇ The value is between 0.94 and 1.

05. The polyvinyl chloride-derived hard carbon material according to claim 16, characterized in that it satisfies one or more of the following conditions.

19. Use of a polyvinyl chloride-derived hard carbon material in a battery according to any one of claims 16 to 18.

20. A battery characterized by containing a polyvinyl chloride-derived hard carbon material as described in any one of claims 16 to 18.

21. A method for manufacturing hard carbon material, The process includes the steps of: mixing a halogen-containing polymer powder and a thermoplastic resin, heating and melting the mixture, and then obtaining the mixture after cooling; next, mixing the mixture with a reducing metal, and then performing dehalogenation by heating at 100 to 400°C for 2 to 12 hours under an inert gas shield to obtain a dehalogenated sample; and finally, washing, drying, and carbonizing the dehalogenated sample to obtain a hard carbon material. The thermoplastic resin is polypropylene and / or polyethylene, and the mass ratio of the thermoplastic resin to the halogen-containing polymer powder is 2 to 10%. When the reducing metal is an alkali metal in its elemental form, the molar ratio of halogen atoms to the reducing metal in the halogen-containing polymer powder is 1:(1-3). A method characterized in that, when the reducing metal is an alkaline earth metal in its elemental form, the molar ratio of halogen atoms in the halogen-containing polymer powder to the reducing metal is 1:(0.5 to 1.5).

22. The halogen-containing polymer powder is polyvinyl chloride (PVC) and / or polyvinylidene chloride (PVDC). Preferably, the viscosity number K value of the polyvinyl chloride is 50 to 80, for example, 62 to 60. The method for producing a hard carbon material according to claim 21, characterized in that the particle size of the halogen-containing polymer powder is 0.1 to 1 μm.

23. The alkali metal element is Na and / or K. The method for producing a hard carbon material according to claim 21, characterized in that the alkaline earth metal element is one or more of Mg, Ca, and Ba.

24. When the reducing metal is an alkali metal in its elemental form, the molar ratio of halogen atoms in the halogen-containing polymer powder to the reducing metal is 1:(1-2), for example, 1:1.1, 1:1.2, or 1:1.

3. The method for producing a hard carbon material according to claim 21, characterized in that, when the reducing metal is an alkaline earth metal in elemental form, the molar ratio of halogen atoms in the halogen-containing polymer powder to the reducing metal is 1:(0.5 to 1), for example, 1:0.

55.

25. The melt flow index of the aforementioned polypropylene is 10 to 40 g / 10 min, for example, 35 g / 10 min. And / or, the melt flow index of the polyethylene is 10 to 40 g / 10 min, for example, 25 g / 10 min. The method for producing a hard carbon material according to claim 21, characterized in that the mass ratio of the thermoplastic resin to the halogen-containing polymer powder is 2 to 8%, for example, 5%.

26. The heating and melting temperature is 100 to 140°C, for example, 120°C. The method for producing a hard carbon material according to claim 21, characterized in that the heating and melting time is 1 to 4 hours, for example, 2 hours.

27. The temperature for the aforementioned heating dehalogenation is 200 to 400°C, for example, 250°C. And / or, the heating dehalogenation time is 2 to 6 hours, for example, 3 hours. and / or, the carbonization temperature is 600 to 1000°C, for example, 800°C, 850°C or 900°C. The method for producing a hard carbon material according to claim 21, characterized in that the carbonization time is 0.5 to 10 hours, preferably 3 to 6 hours, for example 4 hours.

28. A hard carbon material characterized by being manufactured according to the method for manufacturing a hard carbon material described in any one of claims 21 to 27.

29. Use of the hard carbon material in a secondary battery according to claim 28.

30. A secondary battery characterized by containing the hard carbon material described in claim 28.

Images