Mesoporous carbon structure, electrode material comprising same, and method for manufacturing mesoporous carbon structure

Abstract

A mesoporous carbon structure according to an embodiment of the present invention includes a plurality of pores, wherein the volume of mesopores having a size of 2-50 nm constitutes at least 70% of the total volume of the pores, and the total specific surface area is 500 m2 / g or more.

Description

Medium-pore carbon structure, electrode material including the same, and method for manufacturing a medium-pore carbon structure

[0001] The present invention relates to a mesoporous carbon structure, an electrode material comprising the same, and a method for manufacturing a mesoporous carbon structure. More specifically, the invention relates to a carbon structure in which mesoporous regions are uniformly developed, an electrode material comprising the same, and a method for manufacturing a carbon structure. Furthermore, the invention relates to a method for manufacturing a mesoporous carbon structure in which the process is simplified and productivity is improved.

[0002] Recently, the use of porous carbon structures as electrode materials to enhance the efficiency of secondary batteries and energy storage systems has been attracting attention. In particular, silicon-containing electrode materials are establishing themselves as key materials for next-generation battery technology because they can provide high energy density.

[0003] To utilize silicon as an electrode material, it is required to ensure uniformity and efficiency of silicon deposition on carbon structures, but there are various difficulties in achieving this.

[0004] First, if the pore size and distribution of the porous carbon structure are not uniform, silicon is prone to excessive accumulation in specific areas or the formation of voids; such non-uniform deposition can hinder the flow of lithium ions and increase localized electrochemical reactions, thereby degrading electrode performance.

[0005] In addition, silicon may penetrate into the mesopores of the carbon structure and block them. In this case, the diffusion path of lithium ions is restricted, which negatively affects charging and discharging speeds and capacity, and can significantly reduce efficiency during high-speed charging and discharging.

[0006] Furthermore, silicon can significantly expand in volume as it combines with lithium during the charging process. This induces repeated expansion and contraction on the surface of the carbon structure, which can lead to the destruction of the silicon layer or delamination from the electrode. In this case, not only does the silicon deposition efficiency decrease, but the cycle life and stability of the electrode can also be significantly degraded.

[0007] In addition, porous carbon structures have low bonding strength with silicon, making it prone to detachment of the silicon layer during charging and discharging, which poses difficulties for long-term use.

[0008] Therefore, there is an urgent need for technical measures to solve the aforementioned problems and enhance the potential for utilizing silicon as an electrode material.

[0009] Meanwhile, existing porous carbon structure manufacturing processes are primarily wet processes that use a large amount of solvent to mix precursors. These solvents must be removed during the process, which can lead to environmental pollution problems due to solvent treatment and act as a factor in increasing process costs.

[0010] One aspect of the present invention for solving the aforementioned problem aims to provide a carbon structure in which the region of intermediate pores is uniformly developed, thereby increasing silicon deposition efficiency and stability, and further providing an electrode material with improved charge / discharge life and performance.

[0011] In addition, the purpose is to provide a method for manufacturing carbon structures that simplifies the process and increases productivity by using a solvent-free dry process and omitting the conventional activation step.

[0012] The technical problems to be solved in this document are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this invention belongs from the description below.

[0013] As a means for achieving the above-mentioned purpose, a mesoporous carbon structure according to one embodiment of the present invention comprises a plurality of pores, wherein the volume ratio occupied by mesoporous pores having a size of 2 to 50 nm of the total volume occupied by the pores is 70% or more, and the total specific surface area is 500 m² 2 It has more than / g.

[0014] The specific surface area of ​​the above medium pores is 40% or more of the total specific surface area.

[0015] The total volume occupied by the above pores is 0.7cc / g or more.

[0016] A medium-pore carbon structure according to one embodiment of the present invention is formed by carbonizing a carbon precursor mixture through a single heat treatment, and the single heat treatment is a solvent-free dry process.

[0017] The above carbon precursor mixture includes a polymer precursor, a crosslinking agent, and a surfactant.

[0018] A silicon-carbon containing electrode material according to one embodiment of the present invention comprises a carbon structure having a volume ratio of 70% or more of the total pore volume and a coating layer formed on the surface of the carbon structure, wherein the coating layer contains 17 to 60% of Si and other impurities in weight percent, and the size of the mesopores is 2 to 50 nm.

[0019] The total volume occupied by the pores in the carbon structure is 0.7 cc / g or more, and the volume ratio of the mesopores in the total volume occupied by the pores is 70% or more.

[0020] The total specific surface area of ​​the above carbon structure is 500m² 2 It has a value of / g or more, and the specific surface area of ​​the above medium pores relative to the above total specific surface area is 40% or more.

[0021] A silicon-carbon containing electrode material according to one embodiment of the present invention has a discharge capacity of 1,600 mAh / g or more and an initial Coulomb efficiency (ICE) of 80% or more.

[0022] A method for manufacturing a mesoporous carbon structure according to one embodiment of the present invention comprises the steps of: preparing a carbon precursor mixture comprising a polymer precursor, a crosslinking agent, and a surfactant; and heat-treating the carbon precursor mixture to carbonize it. The carbon structure after the carbonization step is completed comprises a plurality of pores, and the volume ratio of mesoporous pores having a size of 2 to 50 nm to the total volume occupied by the pores is 70% or more.

[0023] The above carbon precursor mixture comprises, in weight percent, 20 to 40 percent polymer precursor, 10 to 20 percent crosslinking agent, 40 to 70 percent surfactant, 5 percent or less solvent, and other impurities including additives.

[0024] The above polymer precursor is any one of a phenolic substance, a hydrocarbon polymer, or a polysaccharide substance.

[0025] The above crosslinking agent is any one of terephthalaldehyde, formaldehyde, glutaraldehyde, epoxy resin, hexamethylenetetramine, and benzaldehyde.

[0026] The above surfactant is any one of a polyoxyethylene block copolymer, a Tween-series surfactant, or an ionic surfactant.

[0027] The above polymer precursor is resorcinol, the above crosslinking agent is terephthalaldehyde (TPA), and the above surfactant may be F127 (PEO-PPO-PEO).

[0028] The above carbonizing step is,

[0029] After heating the above carbon precursor mixture to 400℃ at a heating rate of 1℃ / min,

[0030] A step of producing an intermediate product by maintaining at 400℃ for 3 hours or more;

[0031] A step of heating the above intermediate product to 1000℃ at a heating rate of 5℃ / min and maintaining it for 3 hours or more to produce a carbide; and

[0032] The method includes the step of manufacturing the carbon structure by air-cooling the above carbide,

[0033] The above-mentioned intermediate pores of the carbon structure are formed as the surfactant decomposes during the carbonization step.

[0034] The total specific surface area of ​​the above-mentioned carbon structure after carbonization is 500m² 2 It has a value of / g or more, and the specific surface area of ​​the above medium pores relative to the above total specific surface area is 40% or more.

[0035] The carbon structure after carbonization is complete aggregates to form a solid lump carbonized material, and after the carbonization step, further includes a step of crushing the carbonized material.

[0036] The method further includes a step of aging the mixture between the step of preparing a carbon precursor mixture and the step of carbonizing, wherein in the step of aging the mixture, the surfactant included in the mixture forms a micelle structure and self-assembles.

[0037] According to one aspect of the present invention, the region of the mesopores of the carbon structure is uniformly developed, thereby increasing silicon deposition efficiency and stability, and furthermore, the charge / discharge life and performance of the electrode material can be improved.

[0038] In addition, by using a solvent-free dry process and providing a manufacturing method that omits the conventional activation process, the carbon structure manufacturing process can be simplified and the productivity of the carbon structure can be increased.

[0039] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0040] FIG. 1 is a flowchart of a method for manufacturing a carbon structure according to one embodiment of the present invention.

[0041] Figure 2 is a diagram briefly illustrating the manufacturing process of a carbon structure.

[0042] Figure 3 is a diagram showing examples of constituent materials of a carbon precursor mixture in chemical structural formulas.

[0043] Figure 4 is a flowchart of a conventional method for manufacturing a carbon structure.

[0044] Figure 5 is a graph showing the initial discharge capacity of an electrode material according to an embodiment of the present invention.

[0045] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0046] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof.

[0047] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense. For instance, singular expressions in this specification include plural expressions unless the context clearly indicates an exception.

[0048] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0049] Hereinafter, a mesoporous carbon structure according to one embodiment of the present invention, a silicon-carbon containing electrode material including the same, and a method for manufacturing a mesoporous carbon structure will be described in detail.

[0050] FIG. 1 is a flowchart of a method for manufacturing a carbon structure according to an embodiment of the present invention, and FIG. 2 is a diagram briefly illustrating the manufacturing process of a carbon structure.

[0051] Referring to FIGS. 1 and 2, a method for manufacturing a carbon structure according to one embodiment of the present invention comprises the steps of: preparing a carbon precursor mixture (S1); aging the carbon precursor mixture (S2); heat-treating the carbon precursor mixture to carbonize it (S3); and crushing the carbonized material (S4).

[0052] In the step (S1) of preparing a carbon precursor mixture, the carbon precursor mixture (MT) comprises, in weight percent, 20 to 40 percent polymer precursor (CP), 10 to 20 percent crosslinking agent (CL), 40 to 70 percent surfactant (SF), 5 percent or less solvent, and other impurities including additives. The polymer precursor (CP) combines with the crosslinking agent (CL) to form the carbon skeleton of the carbon structure (MR) described later, and acts as the main carbon raw material for the carbon structure (MR).

[0053] In another embodiment of the present invention, the polymer precursor (CP) may be mixed with other functional materials or additives to contribute to controlling electrical conductivity or surface chemical activity, etc.

[0054] The content of the polymer precursor (CP) may be 20 to 40%. Since the amount of the polymer precursor (CP) determines the final amount of carbon obtained after carbonization, if the content of the polymer precursor (CP) is less than 20%, the carbonization rate is low and the amount of carbon obtained may be very low. In this embodiment, since the yield may affect process efficiency, it is desirable that the sum of the weights of the polymer precursor and the crosslinking agent relative to the total weight of the solids input be at least 30%.

[0055] In one embodiment of the present invention, the polymer precursor (CP) may be any one of a phenolic material, a hydrocarbon polymer, or a polysaccharide material. In a preferred embodiment, the polymer precursor (CP) may be resorcinol. In FIG. 3, examples of constituent materials of a carbon precursor mixture (MT) are illustrated by their chemical structural formulas.

[0056] The crosslinking agent (CL) plays a role in enhancing the structural stability of the final carbon structure (MR) by binding with the polymer precursor (CP). The crosslinking agent (CL) plays a role in promoting the bonding between the polymer precursors (CP).

[0057] The content of the crosslinking agent (CL) may be 10 to 20%. If the content of the crosslinking agent (CL) exceeds 20%, the crosslinking bonds between the polymer precursor (CP) molecules are formed too tightly, which reduces the empty space within the structure and may result in an excessive reduction in pore volume. On the other hand, if the content of the crosslinking agent (CL) is less than 10%, the bonds between the polymer precursor (CP) molecules may not be sufficiently formed. This may result in a porous structure lacking structural stability, or pore formation may not occur properly, making it impossible to obtain the pore size and distribution targeted by the present invention.

[0058] In one embodiment of the present invention, the crosslinking agent (CL) may be any one of terephthalaldehyde (TPA), formaldehyde, glutaraldehyde (GA), epoxy resin (ER), hexamethylenetetramine (HMTA), and benzaldehyde (BzA). In a preferred embodiment, the crosslinking agent may be terephthalaldehyde (TPA).

[0059] The surfactant (SF) plays a role in forming and controlling the structure of the pores (PR) to be described later. The surfactant (SF) acts as a solid template, thereby determining the size and location of pore formation of the pores (PR). According to the present embodiment, the size and arrangement of the pores formed can be controlled by adjusting the concentration or molecular structure of the surfactant (SF).

[0060] The content of the surfactant (SF) may be 40 to 70%. If the content of the surfactant (SF) exceeds 70%, pores may be excessively formed during the carbonization process, and the pores may not be maintained stably, may migrate, or the structure may be abnormally deformed. For example, the pore size may become too large, reducing mechanical stability, or the pores themselves may collapse, making it difficult to obtain the desired structure. On the other hand, if the content of the surfactant (SF) is less than 40%, pore formation may not occur sufficiently, resulting in a decrease in the specific surface area. Additionally, the volume of the generated pores may also decrease, making it impossible to form the target mesoporous structure. In one embodiment of the present invention, the surfactant may be any one of a polyoxyethylene block copolymer, a Tween-series surfactant, or an ionic surfactant. In a preferred embodiment, the surfactant may be F127 (PEO-PPO-PEO).

[0061] According to an embodiment of the present invention, the carbon precursor mixture (MT) may contain 5% by weight or less of a solvent, and in another embodiment of the present invention, the carbon precursor mixture (MT) may not contain a solvent.

[0062] The method for manufacturing a carbon structure (MR) according to an embodiment of the present invention may be a solvent-free dry process. In the present invention, a solvent-free dry process is defined as using a carbon precursor mixture (MT) containing 0 to 5 weight percent of solvent. Accordingly, the carbon precursor mixture (MR) of the present invention may be in the form of a solid mixture rather than a solution. In this case, since a separate drying process to vaporize the liquid before the carbonization process (S3) is not performed, time and cost can be saved.

[0063] Once the carbon precursor mixture (MT) is prepared, the carbon precursor mixture (MT) can be aged for a predetermined period of time (S2).

[0064] According to the present embodiment, in the aging step (S2), the polymer precursor (CP) can combine with the crosslinking agent (CL) to form a composite composite (CLP). The crosslinking agent (CL) is a substance that promotes the bonding between the polymer precursor (CP) particles. Since the crosslinking, defined as the bonding between the polymer precursor (CP) and the crosslinking agent (CL) in the composite composite (CLP), is not easily destroyed during the carbonization process, shrinkage or deformation during carbonization can be minimized, thereby maintaining the desired shape and pore structure. Therefore, when the crosslinking increases, the density of the final carbon structure (MR) increases, and the mechanical strength can be improved.

[0065] According to the present embodiment, the formation of the cross-linking bond may begin in the mixing step (S1), and the aging step (S2) may be a process for increasing the composite compound (CLP) by promoting the cross-linking bond.

[0066] In the aging step (S2), the surfactant (SF) is uniformly distributed within the carbon precursor mixture (MT), and the location for pore formation is physically determined.

[0067] As described above, the surfactant (SF) acts as a solid template defined as a physical framework for pore formation. The solid template has a form in which multiple surfactant (SF) particles are arranged. The composite binder (CLP) can surround the outer surface of the solid template of the surfactant (SF). The form in which the composite binder (CLP) surrounds the outer surface of the surfactant (SF) is defined as a template assembly (TA).

[0068] The process of forming the above template assembly (TA) can start in the mixing step (S1), and the formation of the template assembly (TA) can increase in the aging step (S2).

[0069] In the present embodiment, when a solvent of 5% by weight or less, excluding 0, is used, at least a portion of the shape of the solid template of the surfactant (SF) may have a micelle structure. The micelle structure may be formed by the surfactant (SF) self-assembling within the carbon precursor mixture (MT). When the shape of the solid template has a micelle structure, the pores (PR) described later may be formed more uniformly.

[0070] In another embodiment of the present invention, in the step (S1) of preparing a carbon precursor mixture (MT), if a sufficient amount of template assembly (TA) is formed in the carbon precursor mixture (MT), the aging step (S2) may be omitted.

[0071] The template assembly (TA) that has been cured can be carbonized through heat treatment to form a carbon structure (MR) with multiple pores (PR) formed (S3).

[0072] Through the carbonization process (S3), the surfactant (SF) of the template assembly (TA) is decomposed by heat, and a pore (PR) is formed at the location where the surfactant (SF) was located. The pore (PR) can subsequently provide a pathway for the movement of lithium ions when the carbon structure (MR) is used as an electrode material.

[0073] The polymer precursor (CP) of the template assembly (TA) is carbonized through a carbonization process (S3) to form a carbon framework. Specifically, the polymer precursor (CP) is decomposed by heat to generate carbon and release gas. At this time, the cross-links may be partially decomposed or modified during the heat treatment process, and accordingly, the size and distribution of the pores (PR) can be controlled.

[0074] The carbonization step (S3) comprises the steps of: heating a carbon precursor mixture (MT) or a template assembly (TA) from room temperature to 400°C at a rate of 1°C / min under an inert atmosphere, and then maintaining it at 400°C for 3 hours or more to produce an intermediate product; heating the intermediate product to 1000°C at a rate of 5°C / min, and then maintaining it for 3 hours or more to produce a carbonized product; and air-cooling the carbonized product to produce a carbon structure (MR).

[0075] In the carbonization step (S3) above, the intermediate product and the carbide may be in the form of some stage of the process in which the carbon precursor mixture (MT) becomes a carbon structure (MR). For example, the intermediate product may refer to a material in a state where initial pores begin to form as the surfactant begins to thermally decompose. Additionally, the carbide may refer to a material in a state where the surfactant is completely decomposed to form mesopores, and the polymer precursor and crosslinking agent are carbonized to form a carbon skeleton. According to the present embodiment, the carbon structure (MR) after completing the carbonization process (S3) may include a plurality of pores (PR). Additionally, the volume ratio of mesopores to the total volume occupied by the pores (PR) formed in the carbon structure (MR) may be 70% or more. The mesopores are defined as pores having a size of 2 to 50 nm.

[0076] According to the present embodiment, the residual carbon rate, defined as the ratio of carbon in the carbon precursor mixture (MT) after undergoing the carbonization process (S3), may be 20 to 30%. That is, the amount of carbon structure (MR) formed from the original carbon precursor mixture (MT) may be 20 to 30% relative to the amount of the original carbon precursor mixture (MT). If the residual carbon rate is less than 20%, the carbonization efficiency of the material is low, and productivity may be reduced.

[0077] The carbon structure (MR) that has completed carbonization may aggregate with one another to form a solid lump of carbon. The lump of carbon structure (MR) undergoes a grinding step (S4) and can be manufactured into a final particle form. According to the present embodiment, carbon structure (MR) particles with evenly distributed pores can be manufactured through the grinding step (S4), thereby improving the mixability of the product.

[0078] When a carbon structure (MR) manufactured according to an embodiment of the present invention is used as an electrode material, the electrode material may include a carbon structure (MR) and a coating layer formed on the surface of the carbon structure (MR). The coating layer may be formed on the surface of the carbon structure (MR) through a deposition process.

[0079] The coating layer according to an embodiment of the present invention can be formed not only on the outer surface of the carbon structure (MR) but also on the inner wall surface of the mesopore (PR). This is because the carbon structure (MR) according to the present invention has a uniformly developed mesopore structure, which facilitates the penetration of silane gas into the mesopore (PR) during Si deposition. The silane gas that has penetrated into the mesopore (PR) is decomposed by heat during the deposition process, and in this process, a coating layer is formed up to the inner wall surface of the mesopore (PR), thereby increasing the Si loading amount, which can contribute to improving the capacity of the electrode material.

[0080] In particular, since the carbon structure (MR) according to the present invention has uniform mesopores (PR) of a size of 2 to 50 nm, a coating layer can be uniformly formed inside the mesopores (PR) during Si deposition. The formation of such a uniform coating layer can effectively relieve stress caused by the volume expansion of Si during the charge-discharge process and improve the structural stability of the electrode material. In addition, since the coating layer formed on the inner wall of the mesopores (PR) is protected by the pore structure, Si can be prevented from detaching during the charge-discharge process. The coating layer according to an embodiment of the present invention may contain 17 to 60% by weight of Si and other impurities. In a more preferred embodiment, the Si content may be 45 to 60 wt%.

[0081] If the Si content is less than 17%, the insufficient silicon deposition reduces the lithium-ion storage capacity, which may lower the energy density of the electrode. Furthermore, even if the carbon structure (MR) contains a sufficient amount of mesopores, insufficient Si deposition may not occur, resulting in inefficient utilization of the pore structure and making it difficult to expect high-capacity characteristics of the electrode material. On the other hand, if the Si content exceeds 60%, the pores may be nearly filled or reduced, leading to a significant decrease in pore volume. This restricts the movement path of lithium ions and may hinder ion diffusion within the electrode. Additionally, if Si is excessively deposited, the specific surface area of ​​the carbon structure (MR) may decrease. This reduces the reaction surface area where lithium ions and silicon can meet, which may lower the charge and discharge rates. Moreover, since silicon is a material with relatively large volume changes during charging and discharging, a higher deposition amount may increase mechanical stress caused by expansion and contraction during the charging and discharging process. Consequently, problems such as cracking of the coating layer or delamination of the coating layer from the carbon structure may occur.

[0082] Figure 4 is a flowchart of a conventional method for manufacturing a carbon structure.

[0083] As illustrated in FIG. 4, according to a conventional method for manufacturing a carbon structure, the carbon precursor mixture is dissolved in a solvent when preparing the carbon precursor mixture. That is, the conventional carbon precursor mixture may be provided in a liquid form containing an amount of solvent exceeding 5 weight%. In this case, a separate drying process may be additionally required prior to the carbonization process (S3'). However, according to an embodiment of the present invention, since a solid carbon precursor mixture is used, a separate drying process is not required after the mixing step (S1).

[0084] In addition, according to the conventional method for manufacturing carbon structures, a step (S4') for activating the carbonized material is required after the carbonization process (S3'). The activation process (S4') is a process that forms or expands pores of the porous carbon material to increase the specific surface area and pore volume. The activation process may result in additional processing time and costs, and may cause problems with non-uniform pore formation.

[0085] Specifically, the conventional carbonization process requires a complex secondary process (activation process) in which the material is heated from room temperature to 1000°C at a heating rate of 5°C / min and maintained for at least 2 hours to carbonize it, followed by mixing a chemical reagent containing alkali metal elements (Na, K, Ca, etc.) into the carbonized powder in an amount of 1 to 6 times the weight of the carbon powder, and then heating again to 1000°C at a heating rate of 5°C / min and maintaining for at least 2 hours. Furthermore, after the activation process, an additional post-treatment process is required, which involves washing with water and drying until the pH reaches the range of 6-8.

[0086] However, according to an embodiment of the present invention, stable decomposition of the surfactant and pore formation can be induced through a first holding step at 400°C, and subsequently, the pore structure can be stabilized through a second holding step at a high temperature. Therefore, according to this embodiment, a uniform mesopore structure can be obtained through a two-step heat treatment without an additional activation process. This simplification of the process can significantly reduce production time and costs, and can provide an environmentally friendly manufacturing method by eliminating chemical reagents used in the activation process and wastewater generated during the cleaning process.

[0087] In the present invention, the ability to obtain a uniform mesopore structure without an additional activation process is attributed to the type and composition of the materials constituting the carbon precursor mixture (MT). Specifically, resorcinol, which is the polymer precursor (CP), terephthalaldehyde (TPA), which is the crosslinking agent (CL), and F127, which is the surfactant (SF), are all materials having similar melting points and exist in a molten state at a temperature of 150°C or lower. At this time, the surfactant (SF) forms a micelle structure in the molten state and self-assembles, and is uniformly arranged while maintaining an appropriate spacing due to the mutual repulsion between the micelles. At the periphery of this micelle structure, the polymer precursor (CP) and the crosslinking agent (CL) combine to form a composite composite (CLP).

[0088] Subsequently, in the temperature range of 350-400°C, as the surfactant (SF) undergoes thermal decomposition while the complex binder (CLP) around the micelle is cured, the space occupied by the surfactant (SF) is converted into pores (PR). At this time, if the content of the surfactant (SF) is excessive, the pores (PR) may merge with each other and the structure may collapse, whereas if it is too low, a sufficient pore volume cannot be secured. Therefore, the uniform pore (PR) distribution obtained in the present invention is attributed to the optimized ratio of surfactant (SF) relative to the polymer precursor (CP) and crosslinking agent (CL).

[0089] Furthermore, if the polymer precursor (CP) and crosslinking agent (CL) are replaced with other materials, internal pores (PR) are not formed well, because the similar melting points of the three materials are a key factor in the aforementioned reaction mechanism. Consequently, the present invention enables the formation of a uniform mesoporous structure without an additional activation process through the selection of appropriate materials and an optimized compositional ratio.

[0090] Table 1 below is a table listing the measured values ​​of residual carbon content, pore volume, specific surface area, and pore size of a carbon structure (MR) manufactured using the manufacturing method of the present invention under conditions of a solvent-free dry process and omission of activation treatment. Examples 1 to 3 correspond to cases where a carbon precursor mixture is manufactured by varying the ratio of additives during the mixing process (S1). As a comparative example, the measured values ​​of residual carbon content, pore volume, specific surface area, and pore size of a carbon structure manufactured using a conventional manufacturing method under conditions of a wet process and activation treatment are also listed.

[0091] Residual carbon content (%) Pore volume (cc / g) Specific surface area (m²) 2 / g) Pore size (PD50, nm) Total residual carbon rate R+T Total pores Fine / Meso Total BET Fine / Meso Comparative Example 1 165 10.46 -49 3.35 -5.8 Comparative Example 2 N.AN.AN.AN.AN.AN.A Comparative Example 3 616 10.00 1 -3.76 -NA Comparative Example 4 32 N.AN.AN.AN.A Example 1 256 20.7 0.142 / 0.5 176 36.9 276.16 / 382.8 5.43 Example 2 266 40.76 80.148 / 0.6 277 2.13 56.44 / 368.8 8.6 Example 3 236 40.75 70.158 / 0.6 86 53.43 87.5 / 284 9.3* R : Resorcinol Weight, T: Terephthalaldehyde (TPA) weight* Micropores: < 2 nm, Mesopores: 2 - 50 nm

[0092] As described in Table 1, the carbon structure (MR) manufactured using the manufacturing method according to the embodiments of the present invention may have a total volume occupied by pores of 0.7 cc / g or more, and a volume occupied by mesopores of 0.5 cc / g or more. Accordingly, according to the embodiments of the present invention, the volume ratio occupied by mesopores in the total volume may be 70% or more. In a more preferred embodiment, the volume ratio occupied by mesopores in the total volume may be greater than 80%, and the volume ratio occupied by micropores in the total volume may be less than 20% (Example 2). In addition, the total specific surface area of ​​the carbon structure (MR) is 500 m² 2 It is greater than / g, and the specific surface area occupied by mesopores is 200m² 2 It may be greater than / g. Accordingly, according to embodiments of the present invention, the specific surface area of ​​the medium pores relative to the total specific surface area may be 40% or more.

[0093] Comparative Example 1 is a case where a conventional general synthesis method was used. In this method, although Resorcinol was used as the polymer precursor, hexamethyltetramine (HMT) was used instead of TPA as the crosslinking agent, and the surfactant F-127 was not used at all. Instead, an additional KOH activation process was performed to form pores. As a result, the total pore volume was 0.46 cc / g, which fell significantly short of the target value of 0.7 cc / g of the present invention, and the specific surface area was 493.35 m² / g, which was lower than the target value of 500 m² / g. In particular, the development of mesopores was so insufficient that the micro / meso ratio, which indicates how developed the mesopores are, was impossible to measure at all.

[0094] In the case of Comparative Example 2, all materials (Resorcinol, TPA, F-127) included within the scope of the embodiments of the present invention were used, but the ratio was not appropriate. In particular, the content of Resorcinol, a polymer precursor that forms the framework of the carbon structure, was used at too low a level of 10%. As a result, the basic carbon framework itself was not properly formed, so most physical properties, such as pore volume and specific surface area, could not be measured (NA). This demonstrates that the use of an appropriate amount of polymer precursor is essential for the formation of a stable structure.

[0095] Comparative Example 3 is a case where the surfactant F-127 was not used at all. Only Resorcinol and TPA were used in a 2:1 ratio, but the results were very poor. The pore volume was 0.001 cc / g, indicating that almost no pores were formed, and the specific surface area was 3.76 m² / g, which is an extremely low level. This proves that the surfactant F-127 plays a decisive role in the formation of mesopores. This means that without a surfactant, mesopores of uniform size cannot be formed.

[0096] Comparative Example 4 is a case where only Resorcinol and F-127 were used in a 1:1 ratio without using the crosslinking agent TPA. In this case as well, most physical properties could not be measured (NA). This shows that without a crosslinking agent, polymer precursors cannot properly connect to each other to form a stable structure.

[0097] In contrast, Examples 1 to 3 of the present invention exhibited excellent characteristics by including all three materials within the scope of the embodiments of the present invention—a polymer precursor (Resorcinol), a crosslinking agent (TPA), and a surfactant (F-127)—in optimal proportions. The total pore volume was 0.7 cc / g or more, and the volume occupied by mesopores was 0.5 cc / g or more, with the proportion of mesopores in the total pores exceeding 70%. Furthermore, the total BET specific surface area showed a high value of 500 m² / g or more, and the specific surface area ratio of mesopores was found to be 40% or more. This demonstrates that the types and optimal contents of each component presented in the present invention are essential for manufacturing carbon structures with a uniform mesopore structure.

[0098] Figure 5 is a graph showing the initial discharge capacity of an electrode material according to an embodiment of the present invention.

[0099] A medium-pore carbon structure was fabricated using a method for manufacturing a medium-pore carbon structure according to an embodiment of the present invention, and an electrode was manufactured using the medium-pore carbon structure in the following manner.

[0100] A slurry was prepared with a ratio of 80% active material, 10% PAA binder, and 10% SuperC65. Subsequently, the slurry was coated onto a Cu foil, followed by drying and compression to fabricate an electrode. At this time, the active material loading amount was 1.3 mg / cm². 2 And, the electrode density after rolling is 1.2 g / cc.

[0101] The initial discharge capacity of the electrode material was measured by the following method.

[0102] The electrolyte was prepared by adding 1.5 wt% VC and 10% FEC to a 1.0 M LiPF6 solution in EC:EMC=3:7. For the charge-discharge conditions, for the initial charge, one charge-discharge cycle was performed by CC-CV charging to 5 mV with a current corresponding to 0.1 C (0.005 C cut-off), followed by CC discharge to 1.5 V with 0.1 C. Subsequently, a 50-cycle charge-discharge test was conducted under the condition of CC-CV charging to 5 mV with a current corresponding to 0.5 C, followed by discharge to 1.0 V. As shown in Fig. 5, the initial discharge capacity of the electrode material according to the embodiment of the present invention may be 1,600 mAh / g or more. Although the capacity appears to gradually decrease over approximately 50 cycles, it was confirmed to have relatively stable performance in terms of durability.

[0103] In addition, the Initial Coulombic Efficiency (ICE) of the electrode material may be 80% or higher. Initial Coulombic Efficiency is defined as an indicator representing the lithium-ion efficiency between the first charge and discharge of the battery, and a high Initial Coulombic Efficiency means that there is less lithium-ion loss during the battery activation process during the first charge. According to an embodiment of the present invention, since the Initial Coulombic Efficiency of the electrode material is 80% or higher, there is less initial capacity loss, and the long-term charge and discharge performance of the battery can be maintained stably.

[0104] Although embodiments of the invention disclosed above have been illustrated and described, the disclosed invention is not limited to the specific embodiments described above, and various modifications may be made by those skilled in the art to which the disclosed invention belongs without departing from the essence claimed in the claims.

Claims

1. Includes multiple qi techniques, The volume ratio of mesopores having a size of 2 to 50 nm to the total volume occupied by the above pores is 70% or more, and Total specific surface area is 500m² 2 A mesopore carbon structure having more than / g.

2. In Paragraph 1, A mesoporous carbon structure in which the specific surface area of ​​the mesoporous pores is 40% or more of the total specific surface area.

3. In Paragraph 1, A mesoporous carbon structure in which the total volume occupied by the above pores is 0.7 cc / g or more.

4. In Paragraph 1, It is formed by carbonizing a carbon precursor mixture through heat treatment, and The above carbon precursor mixture is a medium-pore carbon structure manufactured through a solvent-free dry process.

5. In Paragraph 4, The above carbon precursor mixture is a mesoporous carbon structure comprising a polymer precursor, a crosslinking agent, and a surfactant.

6. A carbon structure comprising mesopores having a volume ratio of 70% or more of the total pore volume; and It includes a coating layer formed on the surface of the carbon structure, and The above coating layer contains 17 to 60% by weight of Si and other impurities, and A silicon-carbon containing electrode material having medium pores of a size of 2 to 50 nm.

7. In Paragraph 6, A silicon-carbon containing electrode material in which the total volume occupied by the pores in the carbon structure is 0.7 cc / g or more, and the volume ratio occupied by the mesopores in the total volume occupied by the pores is 70% or more.

8. In Paragraph 6, The total specific surface area of ​​the above carbon structure is 500m² 2 A silicon-carbon containing electrode material having a specific surface area of ​​40% or more relative to the total specific surface area.

9. In Paragraph 6, Silicon-carbon containing electrode material having an initial discharge capacity of 1,600 mAh / g or more and an initial Coulomb efficiency (ICE) of 80% or more.

10. A step of preparing a carbon precursor mixture comprising a polymer precursor, a crosslinking agent, and a surfactant; and The method includes the step of heat-treating the carbon precursor mixture to carbonize it. A method for manufacturing a mesoporous carbon structure in which the carbon structure, after the carbonization step is completed, comprises a plurality of pores, and the volume ratio of mesoporous pores having a size of 2 to 50 nm to the total volume occupied by the pores is 70% or more.

11. In Paragraph 10, A method for manufacturing a mesoporous carbon structure, wherein the carbon precursor mixture comprises, in weight percent, 20 to 40 percent polymer precursor, 10 to 20 percent crosslinking agent, 40 to 70 percent surfactant, 5 percent or less solvent, and other impurities including additives.

12. In Paragraph 10, A method for manufacturing a mesoporous carbon structure in which the above polymer precursor is any one of a phenolic material, a hydrocarbon polymer, or a polysaccharide material.

13. In Paragraph 10, A method for manufacturing a mesoporous carbon structure in which the above-mentioned crosslinking agent is any one of terephthalaldehyde, formaldehyde, glutaraldehyde, epoxy resin, hexamethylenetetramine, and benzaldehyde.

14. In Paragraph 10, The above carbonizing step is, After heating the above carbon precursor mixture to 400℃ at a heating rate of 1℃ / min, A step of producing an intermediate product by maintaining at 400℃ for 3 hours or more; A step of heating the above intermediate product to 1000℃ at a heating rate of 5℃ / min and maintaining it for 3 hours or more to produce a carbide; and The method includes the step of manufacturing the carbon structure by air-cooling the above carbide, A method for manufacturing a carbon structure with medium pores, wherein the medium pores of the carbon structure are formed as the surfactant decomposes during the carbonization step.

15. In Paragraph 10, The method further includes a step of aging the mixture between the step of preparing the carbon precursor mixture and the step of carbonizing, and In the step of aging the above mixture, the surfactant included in the mixture forms a solid template, and A method for manufacturing a medium-pore carbon structure in which a composite composite of the polymer precursor and the crosslinking agent is arranged to surround the outer surface of the solid template.

Images