Three-dimensional fibrous storage body, method of manufacturing the same, negative electrode including the same, and secondary battery

Abstract

The present invention discloses a three-dimensional fibrous storage body, a method for manufacturing the same, a negative electrode including the same, and a secondary battery. The present invention comprises a core including a conductive carbon material; an intermediate layer formed to surround the core and including nanoparticles; and a carbon shell formed to surround the intermediate layer, wherein the core has a conductive network structure formed by the conductive carbon material and includes voids formed between the conductive network structures.

Description

Technology Field

[0001] The present invention relates to a three-dimensional fibrous storage body, a method for manufacturing the same, a negative electrode including the same, and a secondary battery. More specifically, the present invention relates to a three-dimensional fibrous storage body capable of achieving a high nanoparticle content while suppressing volume expansion occurring in the negative electrode, a method for manufacturing the same, a negative electrode including the same, and a secondary battery. Background Technology

[0003] The demand for high-energy-density secondary batteries is continuously increasing due to the performance advancement of mobile devices and the proliferation of electric vehicles and energy storage systems. In particular, there is a growing demand for high-capacity anode materials capable of replacing conventional graphite anodes, and among these, silicon is attracting attention as a next-generation anode material due to its high theoretical capacity.

[0004] However, silicon undergoes repeated alloying and dealloying with lithium during the charging and discharging process, resulting in a significant volume expansion of approximately 300%. This volume change leads to the pulverization of silicon particles, the breakdown of the conductive network within the electrode, and increased interfacial instability with the electrolyte. Consequently, this causes problems such as a rapid decrease in capacity relative to the initial capacity and poor lifespan characteristics. Furthermore, the solid electrolyte interface (SEI), which is repeatedly formed and destroyed on the silicon surface, increases irreversible lithium consumption, thereby degrading the efficiency of the battery.

[0005] As a solution to the above problem, a composite cathode structure in which silicon is introduced into a carbon-based structure is proposed. Three-dimensional conductive structures composed of porous carbon, carbon fibers, carbon nanotubes, etc., can improve the electrical connectivity of silicon and provide a mechanical buffering effect. However, in existing structures, problems arise where the volume expansion of silicon cannot be sufficiently accommodated, or where the internal space is not effectively utilized because lithium reacts intensively at the outer edge of the structure. As a result, the utilization rate of the active material in silicon is reduced, and there are limitations in improving long-term cycle characteristics.

[0006] Furthermore, there is a problem in that the silicon content is relatively limited because the proportion of carbon-based materials is often excessively increased to ensure structural stability. As a result, the proportion of capacity contributed by silicon to the entire electrode is reduced, and consequently, there are limitations in realizing high-capacity cathodes. Prior art literature

[0008] Korean Published Patent Application No. 10-2026-0026001, "York-shell structured silicon-carbon composite, method for manufacturing the same, and negative electrode active material including the same" The problem to be solved

[0009] Embodiments of the present invention aim to provide a three-dimensional fibrous storage body capable of effectively buffering volume changes resulting from a nanoparticle-lithium alloy reaction by inducing lithiated nanoparticles to expand into an internal void formed between a conductive network structure and a conductive network structure through a conductive carbon material, a method for manufacturing the same, a negative electrode including the same, and a secondary battery.

[0010] Embodiments of the present invention aim to provide a three-dimensional fibrous storage body capable of forming a three-dimensional structure including a conductive carbon material in the innermost core region of a carbon fiber by introducing nanoparticles into the interior of the carbon shell of a carbon fiber through a triple nozzle electrospinning process using a triple nozzle, a method for manufacturing the same, a negative electrode including the same, and a secondary battery. means of solving the problem

[0012] A three-dimensional fibrous storage body according to an embodiment of the present invention comprises: a core containing a conductive carbon material; an intermediate layer formed to surround the core and containing nanoparticles; and a carbon shell formed to surround the intermediate layer, wherein the core has a conductive network structure formed by the conductive carbon material and includes voids formed between the conductive network structures.

[0013] The above nanoparticles can be electrically connected to the core having the above conductive network structure.

[0014] The above carbon shell may include pores.

[0015] The conductive carbon material may include at least one of carbon nanotubes, graphene, carbon nanofibers, and amorphous carbon.

[0016] The above nanoparticles may include at least one of silicon (Si), germanium (Ge), tin (Sn), tin oxide (SnO2), silicon oxide (SiOx), antimony (Sb), and phosphorus (P).

[0017] The cathode according to an embodiment of the present invention includes a three-dimensional fibrous storage body according to an embodiment of the present invention.

[0018] A secondary battery according to an embodiment of the present invention comprises: a negative electrode comprising a three-dimensional fibrous storage body according to an embodiment of the present invention; a positive electrode positioned opposite to the negative electrode; and an electrolyte disposed between the negative electrode and the positive electrode.

[0019] A method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention comprises the steps of: preparing a core precursor solution containing a conductive carbon material; preparing an intermediate layer precursor solution containing nanoparticles; preparing a carbon shell precursor solution containing a carbon shell polymer; manufacturing a fiber precursor by performing a triple nozzle electrospinning process that simultaneously spins the core precursor solution, the intermediate layer precursor solution, and the carbon shell precursor solution; stabilizing the fiber precursor; and carbonizing the stabilized fiber precursor to manufacture a three-dimensional fibrous storage body. The three-dimensional fibrous storage body comprises: a core containing the conductive carbon material; an intermediate layer formed to surround the core and containing nanoparticles; and a carbon shell formed to surround the intermediate layer.

[0020] The fiber precursor may include: a core precursor dispersed within a polymer matrix and comprising the conductive carbon material; an intermediate layer precursor surrounding the core precursor and dispersed within the polymer matrix, comprising the nanoparticles; and a carbon shell precursor surrounding the intermediate layer precursor and comprising the polymer matrix.

[0021] The above core precursor solution may include the conductive carbon material, a dispersant, a pore-forming polymer, and a solvent.

[0022] In the step of manufacturing the above three-dimensional fibrous storage body, the pore-forming polymer contained within the core precursor may be thermally decomposed to form pores.

[0023] The step of preparing the core precursor solution may further include the step of ultrasonically dispersing the core precursor solution.

[0024] The above intermediate layer precursor solution may include the nanoparticles, pore-forming polymer, and mixed solvent.

[0025] The step of preparing the intermediate layer precursor solution may further include the step of ultrasonically dispersing the intermediate layer precursor solution.

[0026] In the step of manufacturing the above three-dimensional fibrous storage body, the polymer matrix may be carbonized to form a carbon shell.

[0027] The above carbon shell precursor solution may include a carbon shell polymer, a pore-forming polymer, and a solvent.

[0028] In the step of manufacturing the above three-dimensional fibrous storage body, the pore-forming polymer contained within the carbon shell precursor may be thermally decomposed to form pores.

[0029] In the step of manufacturing the fiber precursor, the injection rate of the core precursor solution may be 0.4 mL / h to 1.2 mL / h.

[0030] In the step of manufacturing the fiber precursor, the injection rate of the intermediate layer precursor solution may be 0.6 mL / h to 1.4 mL / h.

[0031] In the step of manufacturing the fiber precursor, the injection rate of the carbon shell precursor solution may be 0.8 mL / h to 1.6 mL / h. Effects of the invention

[0033] According to an embodiment of the present invention, by inducing lithiated nanoparticles to expand into an internal void formed between a conductive network structure and a conductive network structure through a conductive carbon material, a three-dimensional fibrous storage body capable of effectively buffering volume changes due to a nanoparticle-lithium alloy reaction, a method for manufacturing the same, a negative electrode including the same, and a secondary battery can be provided.

[0034] According to an embodiment of the present invention, a three-dimensional fiber-type storage body capable of forming a three-dimensional structure including a conductive carbon material in the innermost core region of a carbon fiber by introducing nanoparticles into the carbon shell of a carbon fiber through a triple nozzle electrospinning process using a triple nozzle, a method for manufacturing the same, a negative electrode including the same, and a secondary battery can be provided. Brief explanation of the drawing

[0036] FIG. 1 is a schematic diagram illustrating a three-dimensional fibrous storage body according to an embodiment of the present invention. FIG. 2 is a manufacturing method illustrating a method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a triple nozzle electrospinning process using a triple nozzle for a three-dimensional fiber-type storage body according to an embodiment of the present invention. Figure 4 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1. Figure 5 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 at an intermediate stage of lithiation. Figure 6 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 in a maximum lithiated state. Figure 7 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 during an intermediate stage of the delithiation process. Figure 8 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 after complete delithiation. Figure 9 is a graph showing the results of the analysis of the long-term cycle driving characteristics of the cathode according to Example 2-1. Figure 10 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-2. Figure 11 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Examples 1-3. FIG. 12 shows the electrochemical characteristics of the three-dimensional fibrous storage body according to Examples 2-3. Figure 13 is an image showing the results of analyzing the cyclic voltage-current (CV) characteristics of a secondary battery according to Example 3. FIG. 14 is an image showing the stability measurement results of a three-dimensional fibrous storage body according to an embodiment of the present invention. Specific details for implementing the invention

[0037] Embodiments of the present invention will be described in detail below with reference to the attached drawings and the contents described therein, but the present invention is not limited or restricted by the embodiments.

[0038] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components or steps mentioned in the description.

[0039] As used herein, terms such as “examples,” “examples,” “aspects,” “examples,” etc., are not to be interpreted as implying that any described aspect or design is superior or more advantageous than other aspects or designs.

[0040] Furthermore, the term 'or' refers to an inclusive or rather an exclusive or. That is, unless otherwise noted or is clear from the context, the expression 'x uses a or b' refers to any one of the natural inclusive permutations.

[0041] Additionally, singular expressions (“a” or “an”) used in this specification and claims should generally be interpreted to mean “one or more” unless otherwise stated or it is clear from the context that they relate to the singular form.

[0042] The terms used in the following description have been selected as common and universal in the relevant technical field, but other terms may exist depending on technological development and / or changes, conventions, preferences of the skilled technician, etc. Therefore, the terms used in the following description should not be understood as limiting the technical concept, but as illustrative terms to explain the embodiments.

[0043] In addition, in specific cases, there are terms arbitrarily selected by the applicant, and in such cases, their detailed meanings will be described in the relevant explanatory section. Therefore, the terms used in the description below must be understood not merely as their names, but based on their meanings and the content throughout the specification.

[0044] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0045] Meanwhile, in describing the present invention, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted. Furthermore, the terminology used in this specification is used to appropriately express embodiments of the present invention, and such terminology may vary depending on the intent of the user or operator, or the conventions of the field to which the invention belongs. Accordingly, the definitions of these terms should be based on the content throughout this specification.

[0047] FIG. 1 is a schematic diagram illustrating a three-dimensional fibrous storage body according to an embodiment of the present invention.

[0048] A three-dimensional fibrous storage body according to an embodiment of the present invention may include a multilayer structure comprising a continuous carbon skeleton on the outer side (preferably, carbon cell (130)), a storage area (preferably, intermediate layer (120)) dispersed therein, a conductive network formed in the core area (preferably, core (110)), and empty spaces (preferably, voids).

[0049] Specifically, a three-dimensional fibrous storage body according to an embodiment of the present invention comprises a core (110) containing a conductive carbon material (111), an intermediate layer (120) formed to surround the core (110) and containing nanoparticles (121), and a carbon shell (130) formed to surround the intermediate layer (120).

[0050] Accordingly, the three-dimensional fibrous storage body according to an embodiment of the present invention can effectively buffer volume changes resulting from nanoparticle-lithium alloy reactions (e.g., silicon nanoparticle-lithium alloy reaction) by inducing lithiated nanoparticles (e.g., lithiated silicon nanoparticles) to expand into an internal void formed between a conductive network structure and a conductive network structure through a conductive carbon material (111, e.g., silicon nanoparticles).

[0051] The three-dimensional fiber-type storage body according to an embodiment of the present invention may have a three-dimensional structure in the form of fibers. Accordingly, the three-dimensional fiber-type storage body according to an embodiment of the present invention improves the permeability of electrolyte within the electrode and increases the utilization rate of the active material of the nanoparticle (121), making it advantageous for application as a high-capacity cathode. Accordingly, the three-dimensional fiber-type storage body according to an embodiment of the present invention may have excellent applicability as a high-energy-density cathode material for secondary batteries.

[0052] Specifically, conventional core-shell structures consisting of simple silicon and carbon, as well as core-shell structures in which silicon and carbon are mixed, had the problem of exhibiting low actual capacity due to a low silicon content relative to the overall structure. Additionally, even if there was space to prevent stress relief in the shell portion during volume expansion caused by lithiation, there was a problem in that a medium was absent to facilitate expansion into the interior of the structure.

[0053] However, the three-dimensional fiber-type storage body according to an embodiment of the present invention may have a three-dimensional fiber-type storage body structure comprising a conductive carbon material (111), nanoparticles (121), and carbon fibers, and may have a structure in which a core (110) and a carbon shell (130) are formed inside the carbon fibers.

[0054] In the core (110) of the carbon fiber, a conductive network structure is formed by intertwining conductive carbon materials (111), and fine pores are formed between the conductive carbon materials (111) to form a porous structure. This structure forms a continuous conductive path inside the three-dimensional fiber-type storage body according to an embodiment of the present invention and simultaneously provides internal clearance space, which can buffer the volume change of the active material that occurs during the charging and discharging process.

[0055] A storage region of an intermediate layer (120) in which nanoparticles (121) are dispersed is formed on the outer side of the core (110), and the nanoparticles (121) exist in a dispersed form between the carbon-based matrix of the core (110) and the carbon walls of the carbon shell (130) so as to maintain a state of being electrically connected to an electrically conductive network.

[0056] Additionally, a carbon shell (130) made of carbon fiber is formed on the outside of the carbon fiber to provide mechanical stability to the entire fiber structure and to form an external conduction path. The pores (p2) contained in the carbon shell (130) can additionally perform the role of assisting in the transport of lithium ions from the outside.

[0057] Accordingly, the three-dimensional fiber-type storage body according to an embodiment of the present invention can form a multilayer structure in which a conductive network structure in the inner region, a nanoparticle storage structure in the middle region, and a carbon fiber shell structure in the outer region are continuously connected to each other.

[0058] Accordingly, the three-dimensional fiber-type storage body according to the embodiment of the present invention is a three-dimensional fiber-type storage body structure comprising a core conductive network based on a conductive carbon material (111), an internal pore structure, a storage body region in which nanoparticles (121) are dispersed, and an external pore (p2), and is structurally and functionally different from the conventional simple silicon and carbon core-shell structure and the core-shell structure in which silicon and carbon are mixed.

[0059] Hereinafter, each component of the three-dimensional fibrous storage body according to an embodiment of the present invention will be described in detail.

[0061] A three-dimensional fibrous storage body according to an embodiment of the present invention includes a core (110) containing a conductive carbon material (111).

[0062] The core (110) has a conductive network structure formed by a conductive carbon material (111) and includes voids formed between the conductive network structures.

[0063] Accordingly, the three-dimensional fiber-type storage body according to the embodiment of the present invention can suppress excessive side reactions on the surface of nanoparticles (121) by effectively separating and controlling the movement paths of lithium ions and electrons through a conductive network structure formed in the core (110).

[0064] A conductive carbon material (111, e.g., carbon nanotube) included in the core (110) can simultaneously provide internal pores and electrical conduction paths that act as buffers for the volume expansion of nanoparticles (121, e.g., silicon nanoparticles), thereby dispersing the volume expansion of the three-dimensional fibrous storage material that occurs during the charging and discharging process into the internal space and inducing the reaction within the electrode into the fiber.

[0065] Accordingly, the three-dimensional fibrous storage body according to an embodiment of the present invention can alleviate local reaction concentration and maintain the continuity of the conductive network through a structure comprising a conductive carbon material (111) in the core (110).

[0066] According to an embodiment of the present invention, the three-dimensional fiber-type storage body can be adjusted to accommodate the internal volume expansion of the structure that occurs during lithiation depending on the width of the voids included in the core (110). For example, the width of the voids included in the core (110) can be adjusted depending on the size and content of the conductive carbon material (111) included within the core (110).

[0067] Since the voids included in the core (110) are voids between conductive carbon materials (e.g., carbon nanotubes), the conductive carbon materials (e.g., carbon nanotubes) may not be arranged uniformly and in a uniform shape in the core (10).

[0068] However, if the voids included in the core (110) are too small, a problem may arise in that they cannot stably accommodate the volume expansion that occurs during lithiation, and if the voids are too large, a problem may arise in that the connectivity with the nanoparticles (121) is reduced, resulting in lower electrical conductivity.

[0069] The thickness of the conductive carbon material (111) may be 5 nm to 50 nm. If the thickness of the conductive carbon material (111) is less than 5 nm, a problem may arise in that the portion directly connected to the nanoparticles (121) of the intermediate layer (120) is reduced. If it exceeds 50 nm, a problem may arise in that the voids capable of accommodating volume expansion during lithiation are reduced, thereby increasing the stress concentrated in the carbon shell (130). Preferably, the thickness of the conductive carbon material (111) may be 20 nm.

[0070] Depending on the width of the voids included in the core (110), the content of the conductive carbon material (111) included in the core (110) and the nanoparticles (121) included in the intermediate layer (120) can be controlled.

[0071] The width of the core (110) may be 200 nm to 800 nm. If the width of the core (110) is less than 200 nm, there is a problem that there may be insufficient space to accommodate expansion during lithiation, and if it exceeds 800 nm, there is a problem that the amount of nanoparticle storage that can be stored is too small compared to the size of the three-dimensional fiber-type storage.

[0072] According to an embodiment of the present invention, the degree to which the pores present in the core (110) and the nanoparticles (121) present in the intermediate layer (120) and the conductive nanomaterial (111) are physically connected can be controlled (e.g., increased or decreased) depending on the content of the conductive carbon material (111).

[0073] The content of the conductive carbon material (111) included in the three-dimensional fiber-type storage body according to an embodiment of the present invention may be 0.1% by weight to 5% by weight. If the content of the conductive carbon material (111) is less than 0.1% by weight, there is a problem that the conductive carbon material (111) that induces the direction inward during volume expansion is insufficient, and thus stress concentration in the carbon shell (130) may increase. If it exceeds 5% by weight, the aggregation portion of the conductive carbon material (111) increases, and the problem of the fiber bursting during electrospinning may increase rapidly.

[0074] The conductive carbon material (111) may be manufactured by carbonizing a polymer, but it may also include a conductive carbon material that induces a direction of volume expansion and forms a void between them.

[0075] Additionally, the conductive carbon material (111) can provide an internal space and form an electron transport path, buffer volume changes occurring during the repeated alloying and dealloying processes of the storage body, and contribute to suppressing the breakdown of the conductive network within the electrode.

[0076] The conductive carbon material (111) is not particularly limited as long as it is a structure capable of providing internal voids, having electrical conductivity, and forming electron transport paths, but for example, the conductive carbon material (111) may include at least one of carbon nanotubes, graphene, carbon nanofibers, and amorphous carbon.

[0077] Graphene may include a porous or layered structure. Amorphous carbon may include amorphous carbon containing a porous network.

[0078] Preferably, the conductive carbon material (111) may include carbon nanotubes. The carbon nanotubes may include at least one of single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT).

[0079] Carbon nanotubes can secure structural stability by forming an electrically conductive network and providing a buffer space, and because they have high electrical conductivity and a long one-dimensional structure, they can form a continuous conductive path by intertwining with each other.

[0080] A three-dimensional fibrous storage body according to an embodiment of the present invention is formed to surround a core (110) and includes an intermediate layer (120) containing nanoparticles (121).

[0081] The nanoparticles (121) may be a negative electrode active material. For example, when a three-dimensional fiber-type storage body according to an embodiment of the present invention is used in a lithium-ion battery, the nanoparticles (121) may be used as a lithium storage body and may undergo an alloying reaction with lithium during charging.

[0082] The nanoparticle (121) can be electrically connected to the core (110) having a conductive network structure.

[0083] The nanoparticles (121) may include various negative electrode storage materials for secondary batteries that undergo a volume change during the charging and discharging process. For example, the nanoparticles (121) may include at least one of silicon (Si), germanium (Ge), tin (Sn), tin oxide (SnO2), silicon oxide (SiOx), antimony (Sb), and phosphorus (P). Preferably, the nanoparticles (121) may include silicon (Si).

[0084] Tin (Sn), tin oxide (SnO2), silicon oxide (SiOx), antimony (Sb), or phosphorus (P) have high theoretical capacities, but electrode stability is degraded due to large volume changes. However, when included in a three-dimensional fibrous storage body according to an embodiment of the present invention, electrode life characteristics can be improved by buffering volume changes using internal space and securing a continuous conduction path.

[0085] The average particle size of the nanoparticle (121) may be 30 nm to 50 nm. If the average particle size of the nanoparticle (121) is less than 30 nm, the resistance during charging and discharging increases, causing the performance of the secondary battery to deteriorate. If it exceeds 50 nm, the stress of the nanoparticle (121) increases, and the volume expansion of the nanoparticle (121) during charging and discharging increases significantly, causing the performance and lifespan of the secondary battery to deteriorate.

[0086] A three-dimensional fibrous storage body according to an embodiment of the present invention can maintain a relatively high content of nanoparticles (110, e.g., silicon nanoparticles) while ensuring mechanical stability through a three-dimensional carbon framework, thereby enabling the realization of high energy density compared to conventional silicon-carbon composite cathodes with excessively high carbon content.

[0087] According to an embodiment of the present invention, at least one of the dispersion density and structural filling degree can be controlled in the three-dimensional fibrous storage body according to the content of nanoparticles (110).

[0088] For example, if the content of nanoparticles (121) becomes too high, aggregation problems may occur within the precursor solution caused by van der Waals forces or electrostatic interactions between the nanoparticles (121). If such problems occur, the stability of fiber formation during electrospinning may be compromised, causing the fibers to burst and making it difficult to create a stable fiber storage body. Additionally, if the content of nanoparticles (121) becomes too high, the space of the core (110) may decrease, which reduces the amount of voids that are conventionally formed between the conductive carbon materials (111), making it difficult to stably receive volume expansion.

[0089] The content of the nanoparticles (121) included in the three-dimensional fiber-type storage body according to an embodiment of the present invention may be 30% to 60% by weight. If the content of the nanoparticles (121) is less than 30% by weight, the capacity of the storage body is reduced and it becomes difficult to connect with the conductive carbon material (111). If the content exceeds 60% by weight, the overvoltage increases in the case of a material with insufficient electrical conductivity and the voids of the core (110) that accept volume expansion decrease.

[0090] The content of nanoparticles (121) in the three-dimensional fiber-type storage body according to an embodiment of the present invention can be controlled according to the thickness of the intermediate layer (120). For example, when the thickness of the intermediate layer (120) is 800 nm, the content of nanoparticles (121) may be about 60 weight%.

[0091] The thickness of the intermediate layer (120) may be 300 nm to 800 nm. If the thickness of the intermediate layer (120) is less than 300 nm, the content of nanoparticles (121) is low, resulting in a lower capacity of the storage body and making physical connection with the conductive carbon material (111) in the core (110) difficult. If the thickness exceeds 800 nm, the overvoltage increases in the case of a material with insufficient electrical conductivity, and the voids in the core (110) that accept volume expansion decrease.

[0092] A three-dimensional fibrous storage body according to an embodiment of the present invention includes a carbon shell (130) formed to surround an intermediate layer (120).

[0093] The carbon shell (130) is manufactured by carbonizing a carbon shell polymer and may be made of a material that has rigidity and electrical conductivity to contain internal materials.

[0094] The carbon shell (130) can serve to provide mechanical stability to the entire fiber structure and form an external conduction path.

[0095] The carbon shell (130) can be formed by carbonizing a polymer used as a carbon shell polymer to form the framework of the shell, and for example, the carbon shell (130) may include at least one of polyacrylonitrile (PAN), polyimide, and phenolic resin.

[0096] The carbon shell (130) may include pores (p2). The pores (p2) formed in the carbon shell (130) may serve to assist in the transport of lithium ions from the outside.

[0097] According to an embodiment of the present invention, the amount and degree of diffusion of carrier ions introduced from outside the three-dimensional fibrous storage body can be controlled according to the width of the pores (p2) included in the carbon shell (130). For example, the width of the pores (p2) included in the carbon shell (130) can be controlled according to the amount of carbon shell polymer that forms them in the precursor solution of the carbon shell (130).

[0098] At this time, the pore-forming polymer may include at least one of styrene acrylonitrile (SAN), polymethyl methacrylate (PMMA), polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), and polystyrene (PS).

[0099] The width of the pore (p2) included in the carbon shell (130) may be 1 nm to 100 nm. If the width of the pore (p2) included in the carbon shell (130) is less than 1 nm, there is a problem that the transport of carrier ions may be difficult, and if it exceeds 100 nm, there is a problem that the mechanical stability of the carbon shell (130) is compromised, causing the destruction of the structure.

[0100] In addition, the amount and size of the pores can be controlled according to the amount of SAN (pore-forming polymer, which is a pore-forming polymer that is removed during carbonization and only the PAN polymer that forms the shell remains after carbonization, thus forming a porous carbon shell) added to the carbon shell (130).

[0101] According to an embodiment of the present invention, the mechanical stability of the fibrous structure (e.g., 3D fibrous storage) can be controlled according to the thickness of the carbon shell (130). For example, when 9.5 wt% of polyacrylonitrile is added to a precursor solution and carbonized, a carbon shell (130) having a thickness of 100 nm can be formed.

[0102] The thickness of the carbon shell (130) may be 100 nm to 300 nm. If the thickness of the carbon shell (130) is less than 100 nm, the stability of the structure is compromised, and there is a problem that the structure collapses during long-term cycling. If it exceeds 300 nm, the nanoparticle (121) content decreases, making it difficult to achieve a high capacity.

[0103] Hereinafter, a cathode according to an embodiment of the present invention comprising a three-dimensional fibrous storage body according to an embodiment of the present invention will be described.

[0105] Conventional silicon anode structures have been reported to suffer from structural collapse within the electrode, disruption of the conduction network, and continuous breakdown of the solid electrolyte interface (SEI) due to excessive volume expansion resulting from the repeated alloying and dealloying of silicon during the charge and discharge process. In particular, when silicon particles are concentrated on the electrode surface or in localized regions, the current distribution within the electrode becomes non-uniform, leading to excessive reactions in specific areas and accelerating side reactions. Furthermore, even if a carbon-based matrix is ​​introduced to address silicon volume changes, there are limitations in ensuring the long-term cycle stability of the electrode if the structural buffering effect is insufficient.

[0106] On the other hand, the cathode according to the embodiment of the present invention is not simply dispersed in a carbon matrix, but forms a three-dimensional silicon-carbon structure in the form of fibers through an electrospinning process and can introduce a structure having stepwise functional separation therein.

[0107] In addition, the cathode according to the embodiment of the present invention can effectively accommodate the volume expansion of silicon through a three-dimensional fibrous storage body according to the embodiment of the present invention, which is divided into a shell, an intermediate layer, and a core, and there is little concern about structural collapse or disconnection of the conductive network during the electrode manufacturing and driving process. Accordingly, the cathode according to the embodiment of the present invention can mitigate local reactions of silicon during the charging and discharging process and maintain a more uniform current distribution within the electrode.

[0108] The negative electrode according to an embodiment of the present invention is manufactured into an electrode shape through a wet casting process and can be applied to a lithium-ion battery.

[0109] According to an embodiment, the cathode according to an embodiment of the present invention may include a current collector and a cathode active material layer attached to the current collector.

[0110] The current collector may include at least one of Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel.

[0111] The cathode active material layer may include a three-dimensional fibrous storage body, a conductive material, and a binder according to an embodiment of the present invention.

[0112] The three-dimensional fibrous storage body according to an embodiment of the present invention may include the same components as the three-dimensional fibrous storage body according to an embodiment of the present invention described in FIG. 1, and the description of the same components is omitted.

[0113] The conductive material may include at least one of activated carbon, carbon black (super-P), graphene, reduced graphene oxide, carbon nanotubes, ketjen black, and vapor-grown carbon fiber (VGCF).

[0114] The binder may include fluorinated resin, thermoplastic resin, ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, natural butyl rubber (NBR), and cellulose-based or styrene-butadiene rubber (SBR).

[0115] Fluorine-containing resins may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride, fluororubber, etc.

[0116] Thermoplastic resins may include polypropylene, polyethylene, polyethylene oxide, polyacrylic acid, etc.

[0117] The cathode can be manufactured by mixing a cathode active material, a binder, and optionally a conductive material to prepare a composition for forming a cathode active material layer, and then applying it to a current collector; since such cathode compositions are widely known in the field, a detailed description is omitted.

[0119] Hereinafter, a secondary battery according to an embodiment of the present invention comprising a three-dimensional fiber-type storage body according to an embodiment of the present invention will be described.

[0121] A secondary battery according to an embodiment of the present invention includes a negative electrode comprising a three-dimensional fiber-type storage body according to an embodiment of the present invention, a positive electrode positioned opposite the negative electrode, and an electrolyte disposed between the negative electrode and the positive electrode.

[0122] The secondary battery may include at least one of a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, a lithium-sulfur battery, a magnesium battery, a calcium battery, a metal-air battery, and a nickel-based battery.

[0123] For example, phosphorus (P), antimony (Sb), or tin (Sn)-based cathodes in sodium ion batteries are known to exhibit high capacity through alloying reactions with sodium, but there have been limitations to their practical application due to large volume expansion and low conductivity. However, the three-dimensional fibrous storage body according to the embodiment of the present invention can mitigate mechanical deformation occurring during the sodium storage process and improve reaction uniformity by dispersing such sodium storage bodies in an internal space and providing a conductive network.

[0124] Accordingly, the three-dimensional fibrous storage body according to the embodiment of the present invention provides a universal cathode capable of simultaneously achieving volume change buffering and maintaining a conductive network regardless of the type or content of the storage body (e.g., nanoparticles), and can be widely applied to high-capacity lithium-ion batteries and sodium-ion batteries.

[0125] The secondary battery according to an embodiment of the present invention may be a half battery or a two-sided battery.

[0126] Hereinafter, a lithium-ion battery, which is an example of a secondary battery according to an embodiment of the present invention, will be described.

[0127] The anode may contain lithium metal.

[0128] The positive electrode may include a positive current collector and a positive active material layer formed on the positive current collector. The positive active material layer may optionally further include a binder and a conductive material together with the positive active material.

[0129] The positive electrode active material may include a compound capable of reversibly absorbing and desorbing lithium ions.

[0130] For example, the positive electrode active material may include lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, vanadium oxide, etc., but is not limited thereto, and any material used as a positive electrode active material in the relevant technical field is acceptable.

[0131] Each positive active material may be a single material or a mixture of two or more materials.

[0132] The current collector, binder, and conductive material included in the anode may be the same as those previously described.

[0133] The anode can be manufactured by mixing an anode active material, a binder, and optionally a conductive material to prepare a composition for forming an anode active material layer, and then applying it to a current collector; since such anode compositions are widely known in the field, a detailed description is omitted.

[0134] The cathode is capable of inserting and releasing lithium ions and may include a three-dimensional fibrous storage body according to an embodiment of the present invention or a cathode according to an embodiment of the present invention.

[0135] The cathode may include a current collector and a cathode active material layer formed on the current collector. The cathode active material layer may optionally further include a binder and a conductive material together with the cathode active material.

[0136] The cathode can be manufactured by mixing a cathode active material, a binder, and optionally a conductive material to prepare a composition for forming a cathode active material layer, and then applying it to a current collector; since such cathode compositions are widely known in the field, a detailed description is omitted.

[0137] Electrolytes that can be used in the manufacture of lithium-ion batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0138] For example, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0139] For example, non-aqueous organic solvents that may be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, ethyl methyl carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate. there is.

[0140] Among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate can be used as high-viscosity organic solvents because they have high dielectric constants and effectively dissociate lithium salts. Additionally, if low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed with these cyclic carbonates in appropriate proportions, an electrolyte with high electrical conductivity can be produced and used.

[0141] Preferably, the non-aqueous organic solvent may be a mixed solvent comprising ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

[0142] Lithium salts can be used as metal salts, and lithium salts are substances that dissolve well in non-aqueous electrolytes; for example, as the anion of the lithium salt, F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one of the following.

[0143] Preferably, the lithium salt may include LiPF6.

[0144] In addition to the electrolyte components, the electrolyte may further include additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. For example, the additives may include haloalkylene carbonate compounds such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), chloroethylene carbonate (CEC), dichloroethylene carbonate (DCEC), bromoethylene carbonate (BEC), dibromoethylene carbonate (DBEC), nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), succinonitrile (SN), adiponitrile (AN), 1,3,6-hexane tricyanide (HTCN), propenesulfone (PST), propanesulfone (PS), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), 2-fluorobiphenyl (2-FBP), pyridine, triethylphosphite, It may include at least one of triethanolamine, cyclic ether, ethylenediamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, and aluminum trichloride.

[0145] According to an embodiment, the secondary battery of the present invention may further include a separator.

[0146] Any separator that separates the positive and negative electrodes and provides a pathway for lithium ions to move can be used.

[0147] In other words, a separator can be used that has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity.

[0148] For example, the separator may include at least one of glass fiber, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene, and may be in the form of a non-woven or woven fabric.

[0149] For example, polyolefin-based polymer separators such as polyethylene and polypropylene are mainly used in lithium-ion batteries, and coated separators containing ceramic components or polymer materials may also be used to ensure heat resistance or mechanical strength.

[0150] According to the embodiments, the separator may optionally be used as a single layer or a multilayer structure. For example, as the separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer membrane of two or more layers thereof may be used, and a mixed multilayer membrane such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc. may be used.

[0151] Rechargeable batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium-polymer batteries depending on the type of separator and electrolyte used; classified into cylindrical, prismatic, coin, and pouch types according to their shape; and divided into bulk and thin-film types according to their size. As the structures and manufacturing methods of these batteries are widely known in this field, a detailed description is omitted.

[0152] A battery module including a secondary battery as a unit cell according to an embodiment of the present invention and a battery pack including the same can be provided. Since the battery module and the battery pack include a secondary battery according to an embodiment of the present invention having high capacity, high rate capability and cycle capability, they can be used as a power source for a medium-to-large device selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

[0153] Hereinafter, a method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention will be described.

[0154] The method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention may include the same components as the three-dimensional fibrous storage body according to an embodiment of the present invention described in FIG. 1, and the description of the same components is omitted.

[0156] FIG. 2 is a manufacturing method illustrating a method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention, and FIG. 3 is a schematic diagram illustrating a triple nozzle electrospinning process using a triple nozzle for a three-dimensional fibrous storage body according to an embodiment of the present invention.

[0157] A method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention can manufacture a three-dimensional fibrous storage body in which nanoparticles are disposed on the inside of a porous carbon shell and a conductive carbon material is formed in a core by using an electrospinning process.

[0158] A method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention comprises the steps of: preparing a core precursor solution containing a conductive carbon material (S210); preparing an intermediate layer precursor solution containing nanoparticles (S220); preparing a carbon shell precursor solution containing a carbon shell polymer (S230); manufacturing a fiber precursor by performing a triple nozzle electrospinning process that simultaneously spins the core precursor solution, the intermediate layer precursor solution, and the carbon shell precursor solution (S240); stabilizing the fiber precursor (S250); and manufacturing a three-dimensional fibrous storage body by carbonizing the stabilized fiber precursor (S260).

[0159] Accordingly, the method for manufacturing a three-dimensional fiber-type storage body according to an embodiment of the present invention can introduce nanoparticles into the interior of the carbon shell of a carbon fiber through a triple nozzle electrospinning process using a triple nozzle (340) and form a three-dimensional structure including a conductive carbon material in the core region, which is the innermost part of the carbon fiber.

[0160] First, the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention proceeds with the step (S210) of preparing a core precursor solution containing a conductive carbon material.

[0161] The core precursor solution may include a conductive carbon material, a dispersant, a pore-forming polymer, and a solvent.

[0162] The content of the conductive carbon material included in the core precursor solution may be 0.1% by weight to 5% by weight. If the content of the conductive carbon material is less than 0.1% by weight, there is a problem that stress concentration in the carbon shell may increase due to a lack of conductive carbon material that induces internal orientation during volume expansion, and if it exceeds 5% by weight, the aggregation of the conductive carbon material increases, which may rapidly increase the problem of the fiber bursting during electrospinning.

[0163] The conductive carbon material may include at least one of carbon nanotubes, graphene, carbon nanofibers, and amorphous carbon.

[0164] The content of the dispersant included in the core precursor solution may be 0.1% to 5% by weight. If the dispersant content is less than 0.1% by weight, there is a problem that it is difficult to prevent the aggregation of the conductive carbon material, and if it exceeds 5% by weight, the viscosity of the precursor solution becomes too thick, which causes a problem that limits electrospinning.

[0165] To reduce the van der Waals forces of the conductive carbon material, a dispersant can be added to the core precursor solution in an amount similar to or greater than that of the conductive carbon material to suppress aggregation of the conductive carbon material and to allow for uniform dispersion. Therefore, the three-dimensional fibrous storage can improve the uniformity of electrical conduction pathways and the distribution of active materials.

[0166] The dispersant may include a nonionic surfactant.

[0167] For example, the dispersant may include at least one of polyacrylate, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl alcohol, polyacrylamide, polyethylene oxide, carboxymethyl cellulose (CMC), and diisopropylamine (DIPA).

[0168] The pore-forming polymer included in the core precursor solution can be used as a viscosity modifier that forms pores while simultaneously controlling viscosity.

[0169] The content of the pore-forming polymer included in the core precursor solution may be 17% to 30% by weight. If the content of the pore-forming polymer is less than 17% by weight, the viscosity of the precursor solution is too low, which causes a problem of limiting electrospinning. If it exceeds 30% by weight, the viscosity of the precursor solution becomes too high, which causes a problem of limiting electrospinning.

[0170] The pore-forming polymer may include at least one of styreneacrylonitrile (SAN), polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyacrylamide (PAM).

[0171] The solvent is an amide-based polar organic solvent such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP); alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; Glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methylpropyl ketone, or cyclopentanone; esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone, etc., may be included, and may include one or a mixture of two or more of these.

[0172] The step of preparing the core precursor solution (S210) may further include the step of ultrasonically dispersing the core precursor solution.

[0173] The core precursor solution can uniformly disperse the conductive carbon material by performing an ultrasonic dispersion process.

[0174] For example, carbon nanotubes have a tendency to aggregate due to strong van der Waals forces, and if aggregation occurs, their dispersibility within the precursor solution may be reduced. If electrospinning is performed using a precursor solution in which such aggregation has occurred, fiber formation may become unstable or the internal structure of the fiber may not be formed uniformly.

[0175] Accordingly, in the step of preparing the core precursor solution (S210), an ultrasonic dispersion process is performed for a long time of 6 hours or more to uniformly disperse the conductive carbon material within the core precursor solution, thereby inducing stable jet formation during the electrospinning process and consequently forming a uniform fiber structure and internal microstructure.

[0176] In the step of ultrasonically dispersing the core precursor solution, the ultrasonically dispersing time may be 6 to 12 hours. If the ultrasonically dispersing time is less than 6 hours, there is a problem of aggregation occurring, and if it exceeds 12 hours, there is a problem of the precursor solution solidifying.

[0177] Afterwards, the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention proceeds to the step (S220) of preparing an intermediate layer precursor solution containing nanoparticles.

[0178] The intermediate layer precursor solution may include nanoparticles, pore-forming polymers, and a mixed solvent.

[0179] The content of nanoparticles included in the intermediate layer precursor solution may be 4% to 16% by weight. If the content of nanoparticles is less than 4% by weight, the amount of nanoparticles present inside the structure decreases, making it difficult to achieve high capacity, and there is a problem that it becomes difficult to make a direct connection with the conductive carbon material (111) of the core (110). On the other hand, if the content of nanoparticles included in the intermediate layer precursor solution exceeds 16% by weight, the amount of nanoparticles relative to the solvent of the precursor solution increases, making it difficult to electrospinning, and the aggregation between nanoparticles increases, causing the fiber to burst during electrospinning.

[0180] The nanoparticles may include at least one of silicon (Si), germanium (Ge), tin (Sn), tin oxide (SnO2), silicon oxide (SiOx), antimony (Sb), and phosphorus (P).

[0181] The content of the pore-forming polymer included in the intermediate layer precursor solution may be 17% to 30% by weight. If the content of the pore-forming polymer is less than 17% by weight, the viscosity of the precursor solution is too low, which causes a problem of limiting electrospinning. If it exceeds 30% by weight, the viscosity of the precursor solution becomes too high, which causes a problem of limiting electrospinning.

[0182] The pore-forming polymer may include at least one of styreneacrylonitrile (SAN), polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polyacrylamide (PAM).

[0183] It may include a mixed solvent. The mixed solvent is an amide-based polar organic solvent such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP); alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methylpropyl ketone, or cyclopentanone; esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone, etc., may be included, and may include one or a mixture of two or more of these.

[0184] According to an example, the mixed solvent may include a first solvent and a second solvent.

[0185] The first solvent can disperse the precursor substances and control the viscosity of the precursor solution.

[0186] For example, the first solvent may include at least one of dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0187] The second solvent can serve to inhibit mixing between the carbon shell and the internal region by rapidly solidifying the polymer when in contact with the carbon shell polymer used as a precursor for the carbon shell.

[0188] For example, the second solvent may include at least one of acetone and ethyl acetate.

[0189] The weight ratio of the first solvent and the second solvent included in the intermediate layer precursor solution may be 9:1 to 5:5. If the weight ratio is less than 5:5, the viscosity of the solution is lowered, and there is a problem that the stability of the precursor solution is compromised during electrospinning. If the ratio exceeds 9:1, there is a problem that it is difficult to rapidly solidify the polymer when in contact with the carbon shell polymer used as a precursor for the carbon shell.

[0190] The step of preparing the intermediate layer precursor solution (S220) may further include the step of ultrasonically dispersing the intermediate layer precursor solution.

[0191] The intermediate layer precursor solution can uniformly disperse nanoparticles by performing an ultrasonic dispersion process.

[0192] For example, silicon nanoparticles have a tendency to aggregate due to strong van der Waals forces, and if aggregation occurs, their dispersibility within the precursor solution may be reduced. If electrospinning is performed using a precursor solution in which such aggregation has occurred, fiber formation may become unstable or the internal structure of the fiber may not be formed uniformly.

[0193] Accordingly, in the step of preparing the intermediate layer precursor solution (S220), an ultrasonic dispersion process is performed for a long time of 6 hours or more to uniformly disperse nanoparticles within the intermediate layer precursor solution, thereby inducing stable jet formation during the electrospinning process and consequently forming a uniform fiber structure and internal microstructure.

[0194] In the step of ultrasonically dispersing the intermediate layer precursor solution, the ultrasonically dispersing time may be 6 to 12 hours, and if the ultrasonically dispersing time is less than 6 hours, there is a problem of aggregation occurring, and if it exceeds 12 hours, there is a problem of the precursor solution solidifying.

[0195] Afterwards, the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention proceeds to the step (S230) of preparing a carbon shell precursor solution containing a carbon shell polymer.

[0196] The carbon shell precursor solution may include a carbon shell polymer, a pore-forming polymer, and a solvent.

[0197] The content of the carbon shell polymer included in the carbon shell precursor solution may be 9.5% by weight to 20% by weight. If the content of the carbon shell polymer is less than 9.5% by weight, the thickness of the carbon shell becomes thin, which causes problems in the stability of the structure during long-term cycling, and if it exceeds 20% by weight, the viscosity of the precursor solution becomes too thick, which causes problems in electrospinning.

[0198] Carbon shell polymers are polymers used to form a carbon skeleton, and carbon shell polymers may include at least one of polyacrylonitrile (PAN), polyimide, and phenolic resin.

[0199] The content of the pore-forming polymer included in the carbon shell precursor solution may be 1% to 5% by weight. If the content of the pore-forming polymer is less than 1% by weight, there is a problem that pores that help transport carrier ions in the carbon shell are not formed properly, and if it exceeds 5% by weight, there is a problem that the stability of the carbon shell is compromised.

[0200] The pore-forming polymer may include at least one of styreneacrylonitrile (SAN), Pluronic F-127, polymethyl methacrylate (PMMA), polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), and polystyrene (PS).

[0201] The solvent is an amide-based polar organic solvent such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP); alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol, or octanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; Glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; ketones such as acetone, methyl ethyl ketone, methylpropyl ketone, or cyclopentanone; esters such as ethyl acetate, γ-butyl lactone, and ε-propiolactone, etc., may be included, and may include one or a mixture of two or more of these.

[0202] Afterwards, the method for manufacturing a three-dimensional fiber-type storage body according to an embodiment of the present invention proceeds to the step (S240) of manufacturing a fiber precursor by simultaneously spinning a core precursor solution, an intermediate layer precursor solution, and a carbon shell precursor solution through a triple nozzle electrospinning process.

[0203] The triple nozzle electrospinning process is a triple nozzle electrospinning process using three syringes (310, 320, 330) and one nozzle, which can form a fiber with a multilayer structure by simultaneously spinning three different types of precursor solutions (core precursor solution, intermediate layer precursor solution, and carbon shell precursor solution).

[0204] In the core, a conductive network structure containing conductive carbon materials is formed, and voids are formed between the conductive carbon materials to form a porous electrically conductive structure. This core provides electrical conduction paths and, by forming internal spaces, can perform a buffering role capable of responding to volume changes of the active material during the charging and discharging process.

[0205] Accordingly, the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention can form a multilayer fiber structure including a conductive carbon material of the core and an internal pore structure through a triple nozzle electrospinning process.

[0206] The fiber precursor may include a core precursor containing a conductive carbon material dispersed within a polymer matrix, an intermediate layer precursor surrounding the core precursor and dispersed within the polymer matrix containing nanoparticles, and a carbon shell precursor surrounding the intermediate layer precursor and containing a polymer matrix.

[0207] The polymer matrix may include at least one of a pore-forming polymer and a carbon shell polymer.

[0208] Pore-forming polymers volatilize during the high-temperature carbonization process after electrospinning, causing some or all of them to disappear, resulting in the formation of pores in the carbon shell portion after carbonization, or allowing only nanoparticles and conductive carbon materials to exist in the intermediate layer and core.

[0209] The carbon shell polymer may include at least one of polyacrylonitrile (PAN), polyimide, and phenolic resin, and the carbon shell polymer may be transformed into a carbon skeleton during a high-temperature carbonization process after spinning, thereby forming the skeleton of the structure after carbonization.

[0210] For example, the fiber precursor may include a pore-forming polymer and a conductive carbon material within the core precursor, a pore-forming polymer and nanoparticles within the intermediate layer precursor, and a carbon shell polymer within the shell precursor. These polymers (pore-forming polymer and carbon shell polymer) may undergo a carbonization process at high temperatures, become carbonized or disappear, and form pores or voids.

[0211] In the triple nozzle electrospinning process, conductive carbon materials are incorporated into the fibers while dispersed within a polymer matrix; subsequently, during the heat treatment process, the carbon shell polymer is carbonized while the carbon nanotube network is maintained. As a result, interconnected conductive pathways are formed within the fibers, which induce volume expansion into the spaces between internal carbon nanotubes when silicon particles expand, thereby alleviating volume expansion stress during lithiation.

[0212] The conductive network structure formed by conductive carbon materials and the voids between the conductive network structures increase the mechanical strength of the fiber's internal structure during lithiation and delithiation, and can serve as a buffer that induces expansion between the voids when lithium is stored in nanoparticles.

[0213] The triple electrospinning process can be carried out using a triple electrospinning device.

[0214] The triple electrospinning device may include a triple nozzle (340) comprising a first syringe (310) into which a core precursor solution is injected, a second syringe (320) into which an intermediate layer precursor solution is injected, and a third syringe (330) into which a carbon shell precursor solution is injected.

[0215] Additionally, the triple electrospinning device may include a drum that collects fibers spun from the triple nozzle (340) and rotates at a constant speed.

[0216] A triple electrospinning process can produce a three-dimensional fibrous storage body by directly introducing a core precursor solution into a triple nozzle (340), and introducing an intermediate layer precursor solution and an outermost carbon shell precursor solution through a tube to electrospinning.

[0217] For example, the triple electrospinning process can be carried out by connecting a first syringe (310) containing a core precursor solution, a second syringe (320) containing an intermediate layer precursor solution, and a second syringe (330) containing a carbon shell precursor solution to a single triple nozzle (340) located in the center, thereby separating and spraying three precursor solutions at once within a single triple nozzle (340).

[0218] Accordingly, the triple electrospinning process involves placing three precursor solutions into three syringes (310, 320, 330) and connecting the syringes (310, 320, 330) to a single nozzle (340) so that three solutions (core precursor solution, intermediate layer precursor solution, carbon shell precursor solution) can be simultaneously spun from the end of the single nozzle (340).

[0219] In the step (S240) of manufacturing a fiber precursor, the thickness of at least one of the core, intermediate layer, and carbon shell can be controlled according to the injection rate of at least one of the core precursor solution, intermediate layer precursor solution, and carbon shell precursor solution.

[0220] In the step of manufacturing a fiber precursor (S240), the injection rate of the core precursor solution may be 0.4 mL / h to 1.2 mL / h. If the injection rate of the core precursor solution is less than 0.4 mL / h, the precursor solution is not properly spun, and if it exceeds 1.2 mL / h, the voltage of the electrospinning becomes too high, causing the fiber to be formed unstably.

[0221] In the step of manufacturing a fiber precursor (S240), the injection rate of the intermediate layer precursor solution may be 0.6 mL / h to 1.4 mL / h. If the injection rate of the intermediate layer precursor solution is less than 0.6 mL / h, the precursor solution is not properly spun, and if it exceeds 1.4 mL / h, the voltage of the electrospinning becomes too high, causing the fiber to be formed unstably.

[0222] In the step of manufacturing a fiber precursor (S240), the injection rate of the carbon shell precursor solution may be 0.8 mL / h to 1.6 mL / h. If the injection rate of the carbon shell precursor solution is less than 0.8 mL / h, the precursor solution is not properly spun, and if it exceeds 1.6 mL / h, the voltage of the electrospinning becomes too high, causing the fiber to be formed unstably.

[0223] The thickness and stability of the fiber (e.g., 3D fibrous storage) can be controlled according to the applied voltage of the triple electrospinning process.

[0224] The applied voltage of the triple electrospinning process can be 10 kV to 20 kV, and if the applied voltage is less than 10 kV, there is a problem that electrospinning does not proceed normally, and if it exceeds 20 kV, there is a problem that the electrospun fiber bursts.

[0225] In the triple electrospinning process, the distance between the triple nozzle (340) and the drum may be 10 cm to 20 cm. If the distance between the triple nozzle (340) and the drum is less than 10 cm, the fibers clump together, making it difficult to form uniform fibers. If the distance exceeds 20 cm, the fibers do not get properly entangled in the drum.

[0226] The thickness of the fiber (e.g., 3D fibrous storage) can be controlled according to the rotational speed of the drum.

[0227] The rotational speed of the drum can be 150 to 400 rpm, and if the rotational speed of the drum is less than 150 rpm, there is a problem that entanglement between fibers may occur, and if it exceeds 400 rpm, there is a problem that the fibers may be damaged during the process of the fibers gathering in the drum.

[0228] In the triple electrospinning process, since lower humidity is preferable, electrospinning can be carried out while maintaining the lowest controllable humidity. If the humidity is too high, there is a problem where the polymer in the electrospinning precursor solution reacts with the water, causing the precursor solution to solidify. Therefore, if the humidity of the triple electrospinning process exceeds 50%, a problem may occur where the precursor solution solidifies during electrospinning. For example, the humidity of the triple electrospinning process may be 1% to 50%, and preferably, the humidity of the triple electrospinning process may be 11% to 15%.

[0229] Afterwards, the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention proceeds with the step (S250) of stabilizing a fiber precursor.

[0230] A method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention can convert a polymer-based fiber formed by a triple nozzle electrospinning process into an electrochemically stable carbon-based structure and perform stepwise heat treatment to stably maintain the fiber structure.

[0231] In the step of stabilizing the fiber precursor (S250), a structural stabilization reaction of the polymer (e.g., polyacrylonitrile polymer) is carried out so that the chain structure can be fixed.

[0232] The step of stabilizing the fiber precursor (S250) can be carried out at a relatively lower temperature than the temperature of the heat treatment (second heat treatment process) carried out during the carbonization process.

[0233] The heat treatment temperature (temperature of the first heat treatment process) in the step of stabilizing the fiber precursor (S250) may be 150°C to 300°C. If the heat treatment temperature is less than 150°C, the stabilization of the carbon shell polymer does not proceed properly, and if the heat treatment temperature exceeds 300°C, there is a problem that the stabilization does not proceed properly due to side reactions with substances contained in the air.

[0234] Finally, the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention proceeds with the step (S260) of manufacturing a three-dimensional fibrous storage body by carbonizing a stabilized fiber precursor.

[0235] In the step (S260) of manufacturing a three-dimensional fibrous storage body, the polymer matrix may be carbonized to form a carbon shell.

[0236] Preferably, in the step (S260) of manufacturing a three-dimensional fibrous storage body, the polymer matrix may be a carbon shell polymer matrix containing a carbon shell polymer.

[0237] For example, polyacrylonitrile is converted into a ladder structure through cyclization, dehydrogenation, oxidation, and crosslinking of nitrile groups (-C≡N) during a heat treatment process, and subsequently, as most non-carbon elements such as hydrogen, nitrogen, and oxygen are removed during a carbonization process in a high-temperature non-oxygen atmosphere, an aromatic carbon structure is formed, and finally, a stable carbon shell can be formed.

[0238] Accordingly, in the step (S260) of manufacturing a three-dimensional fiber-type storage body, a carbonization reaction proceeds so that a carbon fiber structure having a hard carbon shell can be formed.

[0239] In addition, in the step (S260) of manufacturing a three-dimensional fiber-type storage body, the pore-forming polymer contained within the core precursor may be thermally decomposed to form pores, and the pore-forming polymer contained within the carbon shell precursor may be thermally decomposed to form pores.

[0240] Specifically, in the step (S260) of manufacturing a three-dimensional fibrous storage body, the polymer matrix (preferably, carbon shell polymer) is converted into a carbon structure and the pore-forming polymer (e.g., styrene-acrylonitrile copolymer component) is thermally decomposed so that pores are formed in the core and pores are formed in the carbon shell.

[0241] In addition, in the step of manufacturing a three-dimensional fiber-type storage body (S260), the conductive carbon material and nanoparticles maintain their structure due to high thermal stability, and as a result, a carbon fiber structure with a porous structure and a conductive network combined inside can be formed.

[0242] This secondary heat treatment process is not merely a process of carbonizing carbon shell polymers, but can play an important role in improving electrode performance by forming a conductive network and pore structure inside the fiber.

[0243] In the step (S260) of manufacturing a three-dimensional fiber-type storage body, the carbonization process may be carried out at a temperature higher than the heat treatment temperature during the stabilization process (first heat treatment process).

[0244] The heat treatment temperature (temperature of the second heat treatment process) in the step (S260) of manufacturing a three-dimensional fiber-type storage body may be 800°C to 1400°C. If the heat treatment temperature is less than 800°C, a problem may occur in which some polymer matrix (preferably, carbon shell polymer) cannot be carbonized, and if the heat treatment temperature exceeds 1400°C, a problem may occur in which it is difficult to form a stable structure by deviating from the melting point of the nanomaterial.

[0245] Accordingly, through the method for manufacturing a three-dimensional fibrous storage body according to an embodiment of the present invention, a three-dimensional fibrous storage body comprising a core containing a conductive carbon material, an intermediate layer formed to surround the core and containing nanoparticles, and a carbon shell formed to surround the intermediate layer can be manufactured.

[0247] Hereinafter, preferred embodiments of the present invention will be described in detail. However, these embodiments are intended solely to illustrate the present invention, and the scope of the present invention should not be interpreted as being limited by these embodiments.

[0249] Example 1-1

[0250] Silicon nanoparticles with an average particle size in the range of 30–50 nm were used, carbon nanotubes with a thickness of about 20 nm were used, and PAN (Polyacrylonitrile) was used as a precursor for carbon shell formation.

[0251] The precursor solution corresponding to the core region was prepared to contain 0.5 wt% of multi-walled carbon nanotubes, 0.5 wt% of PVP (Polyvinylpyrrolidone) for dispersion thereof, DMF (Dimethylformamide) as a solvent, and 24 wt% of SAN (Styrene-acrylonitrile) for viscosity control.

[0252] The intermediate layer precursor solution on the outer core contained 13.5 wt% silicon nanoparticles and 24 wt% SAN, and DMF and acetone were mixed in a mass ratio of 8:2 and used as solvents. The outermost carbon shell precursor solution was prepared to contain 9.5 wt% PAN, 4.5 wt% SAN, and DMF.

[0253] The precursor solutions were stirred for 12 hours at 80°C and then used for electrospinning. In particular, the intermediate layer precursor solution containing the core region and silicon was subjected to ultrasonic dispersion for an additional 6 hours prior to spinning to ensure that each constituent material was uniformly dispersed.

[0254] During electrospinning, the core solution was supplied at an injection rate of 0.8 mL / h, the silicon solution at 1.0 mL / h, and the shell solution at 1.2 mL / h, and the applied voltage was set to approximately 17 kV. At this time, the distance between the nozzle and the drum was maintained at 15 cm, the drum rotation speed at 300 rpm, and the humidity during the process was controlled within the range of 11–15%.

[0255] The fibers formed by electrospinning were subjected to a stabilization process in a tube furnace at 280°C for 1 hour in an atmospheric environment, followed by a carbonization process at 1,000°C for 5 hours to form a silicon-carbon structure.

[0257] Examples 1-2:

[0258] It was prepared in the same manner as Example 1-1, except that the silicon nanoparticle content was 10 wt%.

[0260] Examples 1-3:

[0261] It was prepared in the same manner as Example 1-1, except that the content of multi-walled carbon nanotubes was 1 wt%.

[0263] Example 2-1

[0264] The storage material prepared in Example 1-1 was mixed with NMP (N-Methyl-2-pyrrolidone) solvent in a mass ratio of 7:1.5:1.5, containing Super P, a conductive material, and PAA (Polyacrylic acid), a binder, and cast to a thickness of about 200 μm on a copper foil with a thickness of 18 μm.

[0265] The cast electrode was dried in a vacuum oven at 60°C for 12 hours and then used as a working electrode. At this time, the electrode loading level was approximately 0.96 mg / cm². 2 (approx. 3.45 mAh / cm² 2 It was set to ).

[0267] Example 2-2:

[0268] It was prepared in the same manner as Example 2-2, except that it includes the storage agent prepared in Example 1-2.

[0270] Example 2-3:

[0271] It was prepared in the same manner as Example 2-2, except that it includes the storage agent prepared in Example 1-3.

[0273] Example 3

[0274] The cathode prepared in Example 2 was used as the cathode, PE (Polyethylene) with a thickness of 15 μm was used as the separator, and a lithium foil with a thickness of 200 μm was used as the counter electrode. As the electrolyte, an electrolyte with a composition of 5 wt% FEC added to an EC / DEC (1:1, v / v) mixed solvent in which 1 M LiPF6 was dissolved was used.

[0276] [Experimental Example 1] Composition and Characteristics of a Three-Dimensional Fiber-Type Storage Body

[0277] Figure 4 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1.

[0278] Referring to Figure 4, it can be seen that a three-dimensional structure is formed in which silicon nanoparticles are densely distributed inside a thin carbon shell, and multi-walled carbon nanotubes are filled in the innermost core region.

[0280] Figures 5 to 8 illustrate a comparison of structural changes during the lithiation and delithiation processes to confirm the buffering role of the core carbon nanotubes.

[0281] Figure 5 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 at an intermediate stage of lithiation.

[0282] Referring to Figure 5, it can be seen that during the intermediate stage of lithiation, silicon preferentially undergoes an alloying reaction with lithium and stores lithium.

[0284] Figure 6 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 in a maximum lithiated state.

[0285] Referring to Fig. 6, in the maximum lithiation state, lithium diffuses along the carbon nanotubes to the center of the structure, filling the empty spaces between the carbon nanotubes.

[0287] Figure 7 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 during an intermediate stage of the delithiation process.

[0288] Referring to Fig. 7, it can be seen that during the intermediate stage of the subsequent delithiation process, the core region containing carbon nanotubes is restored, and lithium is released.

[0290] Figure 8 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-1 after complete delithiation.

[0291] Referring to Fig. 8, it can be seen that the carbon structure maintains its shape without collapsing even after complete delithiation.

[0293] Figure 9 is a graph showing the results of the analysis of the long-term cycle driving characteristics of the cathode according to Example 2-1.

[0294] Figure 9 shows that a half-cell was fabricated and operated using a lithium foil as a counter electrode (see Example 3) to evaluate the electrochemical performance of the structure based on the structural change in which the space is reversibly restored during the delithiation process after the lithium-litichorized silicon expands into the internal empty space of the carbon nanotube.

[0295] Referring to Figure 9, it can be seen that stable performance can be secured even during long-term cycle operation, as it exhibits a high Coulomb efficiency of 99.3% with a capacity retention rate of close to 100% for about 180 cycles under a current density of 0.2 C.

[0297] [Experimental Example 2] Changes in properties of a 3D fibrous storage body according to its composition ratio

[0298] A three-dimensional fibrous storage body according to an embodiment of the present invention can be implemented in various modified forms depending on the compositional ratio of the components of the intermediate layer (e.g., storage body) and the core, and structural and electrochemical properties according to such compositional changes were compared.

[0299] Experimental Example 2 is an example showing that a three-dimensional fibrous storage body according to an embodiment of the present invention can be implemented in various forms depending on the composition ratio of the intermediate layer and the core, and the technical concept of the present invention is not limited to a specific content range. That is, the content of the three-dimensional fibrous storage body according to an embodiment of the present invention or the ratio of conductive carbon material in the core can be appropriately adjusted according to the target capacity of the battery, mechanical stability, manufacturing process conditions, etc.

[0300] Accordingly, the three-dimensional fibrous storage body according to the embodiment of the present invention can be expected to have the effects of mitigating volume changes during the charging and discharging process and improving reaction uniformity within the electrode, provided that it maintains a structural concept based on an outer carbon framework and an internal buffer space, even when the nanoparticle content is relatively low or high, or when the content of the conductive carbon material within the core changes. All such various embodiments and applications resulting from changes in composition are included within the technical scope of the present invention.

[0302] Figure 10 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Example 1-2.

[0303] Referring to Fig. 10, it can be seen that while the shape of the fiber is maintained, the dispersion density and structural filling degree of the internal storage are formed relatively low.

[0305] Figure 11 is an image showing the scanning electron microscope (SEM) measurement results of a three-dimensional fibrous storage body according to Examples 1-3.

[0306] Referring to Fig. 11, it can be seen that the density of the conductive network inside the carbon fiber is improved and the continuity of the core is strengthened.

[0308] Figure 12 is an image showing the results of analyzing the electrochemical properties of a three-dimensional fibrous storage body according to Examples 2-3.

[0309] Referring to Fig. 12, it can be seen that the electrode maintains its internal conduction pathway more stably during repeated charging and discharging, and its electrochemical properties are also expressed normally.

[0311] [Experimental Example 3] Characteristics of a secondary battery containing a three-dimensional fiber-type storage body

[0312] Figure 13 is an image showing the results of analyzing the cyclic voltage-current (CV) characteristics of a secondary battery according to Example 3.

[0313] Referring to Fig. 13, it can be seen that the increase in interfacial resistance is suppressed even after the initial cycle, and almost no change in current response due to irreversible reactions is observed.

[0314] Therefore, it can be seen that the secondary battery according to Example 3 has stable SEI formation and improved stability of the electrode-electrolyte interface.

[0316] FIG. 14 is an image showing the stability measurement results of a three-dimensional fibrous storage body according to an embodiment of the present invention.

[0317] Figure 14 was prepared by the method of Example 1-1, but with the weight ratio of silicon nanoparticles changed.

[0318] Referring to FIG. 14, it can be seen that a three-dimensional fibrous storage body according to an embodiment of the present invention can apply a high weight ratio even when silicon is used as the storage body.

[0319] Generally, in the field of core-shell structured carbon fiber-based silicon anodes, the weight ratio of silicon has been reported to be limited to approximately 50 wt% to ensure structural stability and lifespan characteristics. However, the three-dimensional fibrous storage device according to the embodiment of the present invention can spatially disperse silicon particles and accommodate volume expansion through a structure in which the outer carbon framework, the conductive network of the core region, and the internal empty space are organically combined. Therefore, it can be seen that structural stability can be maintained even when applying a silicon content of approximately 60 wt%, which is a high level compared to conventional technology.

[0321] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited to the above embodiments, and various modifications and variations are possible from this description by those skilled in the art to which the present invention belongs. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof. Explanation of the symbols

[0323] 110: Core 111: Conductive carbon material 120: Intermediate layer 121: Nanoparticles 130: Carbon shell 310: Core precursor solution 320: Intermediate layer precursor solution 330: Carbon shell precursor solution 340: Triple Nozzle p2: Pore d: Distance between triple nozzle and drum

Claims

Claim 1 A three-dimensional fibrous storage body comprising: a core containing a conductive carbon material; an intermediate layer formed to surround the core and containing nanoparticles; and a carbon shell formed to surround the intermediate layer, wherein the core has a conductive network structure formed by the conductive carbon material and includes voids formed between the conductive network structures. Claim 2 A three-dimensional fibrous storage body according to claim 1, characterized in that the nanoparticles are electrically connected to the core having the conductive network structure. Claim 3 A three-dimensional fibrous storage body according to claim 1, wherein the carbon shell comprises pores. Claim 4 A three-dimensional fibrous storage body according to claim 1, characterized in that the conductive carbon material comprises at least one of carbon nanotubes, graphene, carbon nanofibers, and amorphous carbon. Claim 5 A three-dimensional fibrous storage body according to claim 1, characterized in that the nanoparticle comprises at least one of silicon (Si), germanium (Ge), tin (Sn), tin oxide (SnO2), silicon oxide (SiOx), antimony (Sb), and phosphorus (P). Claim 6 A cathode characterized by including a three-dimensional fibrous storage body according to claim 1. Claim 7 A secondary battery characterized by comprising: a cathode including a three-dimensional fibrous storage body according to claim 1; an anode positioned opposite to the cathode; and an electrolyte disposed between the cathode and the anode. Claim 8 A method for manufacturing a three-dimensional fibrous storage body comprising: a step of preparing a core precursor solution containing a conductive carbon material; a step of preparing an intermediate layer precursor solution containing nanoparticles; a step of preparing a carbon shell precursor solution containing a carbon shell polymer; a step of manufacturing a fiber precursor by performing a triple nozzle electrospinning process that simultaneously spins the core precursor solution, the intermediate layer precursor solution, and the carbon shell precursor solution; a step of stabilizing the fiber precursor; and a step of carbonizing the stabilized fiber precursor to manufacture a three-dimensional fibrous storage body, wherein the three-dimensional fibrous storage body comprises: a core containing the conductive carbon material; an intermediate layer formed to surround the core and containing nanoparticles; and a carbon shell formed to surround the intermediate layer. Claim 9 A method for manufacturing a three-dimensional fibrous storage body according to claim 8, wherein the fiber precursor comprises: a core precursor dispersed within a polymer matrix and comprising the conductive carbon material; an intermediate layer precursor surrounding the core precursor and dispersed within the polymer matrix and comprising the nanoparticles; and a carbon shell precursor surrounding the intermediate layer precursor and comprising the polymer matrix. Claim 10 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, wherein the core precursor solution comprises the conductive carbon material, a dispersant, a pore-forming polymer, and a solvent. Claim 11 A method for manufacturing a three-dimensional fibrous storage body according to claim 10, characterized in that, in the step of manufacturing the three-dimensional fibrous storage body, the pore-forming polymer contained within the core precursor is thermally decomposed to form pores. Claim 12 A method for manufacturing a three-dimensional fibrous storage body according to claim 8, wherein the step of preparing the core precursor solution further includes the step of ultrasonically dispersing the core precursor solution. Claim 13 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, characterized in that the intermediate layer precursor solution comprises the nanoparticles, pore-forming polymer, and mixed solvent. Claim 14 A method for manufacturing a three-dimensional fibrous storage body according to claim 8, wherein the step of preparing the intermediate layer precursor solution further includes the step of ultrasonically dispersing the intermediate layer precursor solution. Claim 15 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, characterized in that, in the step of manufacturing the three-dimensional fibrous storage body, the polymer matrix is ​​carbonized to form a carbon shell. Claim 16 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, wherein the carbon shell precursor solution comprises a carbon shell polymer, a pore-forming polymer, and a solvent. Claim 17 A method for manufacturing a three-dimensional fibrous storage body according to claim 16, characterized in that, in the step of manufacturing the three-dimensional fibrous storage body, the pore-forming polymer contained within the carbon shell precursor is thermally decomposed to form pores. Claim 18 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, characterized in that, in the step of manufacturing the fiber precursor, the injection rate of the core precursor solution is 0.4 mL / h to 1.2 mL / h. Claim 19 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, characterized in that, in the step of manufacturing the fiber precursor, the injection rate of the intermediate layer precursor solution is 0.6 mL / h to 1.4 mL / h. Claim 20 A method for manufacturing a three-dimensional fibrous storage body according to claim 9, characterized in that, in the step of manufacturing the fiber precursor, the injection rate of the carbon shell precursor solution is 0.8 mL / h to 1.6 mL / h.

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