Hybrid graphene composite particles

Abstract

The present invention relates to a graphene composite having a structure in which a plurality of primary fine particles and multilayer graphene are mixed, and a hybrid graphene composite particle including secondary fine particles surrounded or coated with the graphene composite, wherein the primary fine particles are attached to the surface or inside of the multilayer graphene, and a portion of the vacant spaces between the primary fine particles are filled with the graphene composite, thereby forming an interconnected structure.

Description

[Technical Field]

[0001] The present invention relates to hybrid graphene composite particles, and more particularly, graphene-based composite materials (hybrid graphene) can be used as negative and positive electrode active materials. [Background technology]

[0002] There are various rechargeable secondary batteries such as lead-acid batteries and nickel-metal hybrid batteries. Among them, lithium-ion batteries (LIBs) are widely used not only as batteries that supply power to portable mobile devices such as smartphones and netbooks, but also as energy supply components for hybrid vehicles, etc., due to their high energy density, high power density, and operating voltage that can withstand long charging and discharging periods.

[0003] The positive electrode active material in lithium-ion batteries is evolving in a variety of ways, improving its performance. However, even if the positive electrode material generates high energy, its efficiency will inevitably decline if the negative electrode material, which stores it, does not support it in balance. In particular, charging time can only be reduced if the negative electrode material is designed to accept lithium ions well during charging. Graphite has long been widely used as the negative electrode active material. Graphite has a layered structure consisting of multiple layers of regularly bonded carbon stacked on top of each other. During the charging process, when lithium ions move from the positive electrode to the negative electrode, the lithium ions that reach the negative electrode are stored between the graphite layers.

[0004] Research is currently underway into new materials that can replace existing negative electrode active materials to improve the performance of lithium-ion batteries. Graphite has poor electrical conductivity, which means long charge / discharge times, and its capacity to bind lithium ions is insufficient, resulting in a low charging capacity.

[0005] Porous carbon materials, which exhibit excellent electrochemical performance, are commonly used as cathode materials for lithium batteries. Korean Patent Publication No. 10-2014-0110572 discloses a cathode for a lithium-air battery, specifically a cathode for a lithium-air battery including a catalyst layer including a first conductive material supported on a binder and a catalyst supported on a second conductive material; and a current collector. The first conductive material and the second conductive material are carbon materials such as graphite, denka black, and ketjen black.

[0006] Currently, research is underway to find new materials that can replace existing cathode active materials in order to improve the performance of lithium-ion batteries. Graphite has low electrical conductivity, which results in long charge / discharge times, and its capacity to bind lithium ions is insufficient, resulting in a low charging capacity.

[0007] Therefore, there is a need to develop new materials that can solve or mitigate the above problems and improve the properties of anode and cathode materials compared to conventional technologies, thereby increasing the charge capacity and battery life of lithium-ion batteries and shortening the charging time. Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem to be solved by the present invention is to solve the problems that conventional lithium ion batteries have, such as long charge / discharge times due to the low electrical conductivity of graphite contained in the negative and positive electrode active material layers, and low charge capacity due to insufficient capacity for lithium ions to bind to them.To this end, the present invention provides hybrid graphene composite particles for lithium ion batteries, which include hybrid graphene having a multi-layer structure of graphene composite material in which metal, semiconductor particles, and silicon are fused and bonded to graphene to form a three-dimensional network. [Means for solving the problem]

[0009] To overcome these problems, the present invention proposes hybrid graphene composite particles in which metal or semiconductor particles are interconnected with graphene multilayers and a network structure including secondary fine particles surrounded or coated therewith is provided, thereby enabling the metal or semiconductor particles to be maintained in a stable state even after repeated charging and discharging. Existing processes for mixing graphene with metal or semiconductor particles simply involve mixing with already-produced graphene, resulting in insufficient organic bonding between the metal or semiconductor particles and the graphene.

[0010] In the present invention, since graphene is produced by mixing primary and secondary fine particles, the surfaces of the primary and secondary fine particles melt and solidify with the graphene, and the fine particles and the graphene are bonded to form a three-dimensional nanostructure.

[0011] In addition, since the formed hybrid graphene composite particles are composed of multi-layer graphene, they have a structural feature in which primary and secondary fine particles are bound to the surface or inside of the multi-layer graphene, and the graphene composite is filled between the silicon fine particles and interconnected.

[0012] The graphene composite having a structure in which a plurality of primary fine particles and multi-layer graphene are mixed and the hybrid graphene composite particle including secondary fine particles surrounded or coated with the graphene composite have the following effects.

[0013] First, the surfaces of the primary and secondary fine particles are completely coated with graphene, which effectively suppresses volume expansion caused by the binding of the fine particles with lithium ions, thereby resolving the problems of metal or semiconductor particles being broken and separated from the electrode due to excessive volume expansion and contraction.

[0014] Second, the multi-layer graphene layers act as a scaffold that fixes the position of primary and secondary microparticles. Graphene theoretically has a tensile strength 200 times stronger than steel, so it does not easily break even when folded or bent. Therefore, when graphene is combined with metal or semiconductor microparticles to form a multi-layer structure, the position of the metal or semiconductor microparticles is fixed, acting as a scaffold that maintains a stable structure even when the metal or semiconductor changes shape during charging and discharging.

[0015] Third, graphene has high electron mobility and current density, which facilitates electron transfer with lithium ions, thereby facilitating electron transfer with metal or semiconductor fine particles, thereby increasing the charge and discharge speed and improving the charge and discharge efficiency of hybrid graphene composite particles.

[0016] To achieve the above technical objectives, the present invention provides hybrid graphene composite particles, which include a graphene composite having a structure in which a plurality of primary fine particles and multilayer graphene are mixed, and secondary fine particles surrounded or coated with the graphene composite, wherein the primary fine particles are attached to the surface or inside of the multilayer graphene, and some of the primary fine particles are bonded and coagulated with each other, and the multilayer graphene has a three-dimensional structure in which multiple layers of graphene are stacked and bent in any direction, and the graphene composite is produced by a photochemical, photothermal irradiation, or heat treatment process, and some of the vacant spaces between the primary fine particles are filled with the graphene composite, resulting in an interconnected structure.

[0017] The present invention also provides hybrid graphene composite particles, characterized in that the primary fine particles are metal or semiconductor particles.

[0018] The present invention also provides hybrid graphene composite particles, characterized in that the surfaces of the primary fine particles melt and solidify with graphene, so that the fine particles and graphene are bonded to form a three-dimensional nanostructure.

[0019] The primary fine particles of the present invention may be made of silver (Ag), silicon (Si), silicon carbide (Si2C, SiC, or SiC2 containing SiCX), silicon oxide (SiO or SiO2 containing SiOX), silicon composite oxide (Si-MgxSiOx), magnesium metasilicate (enstatite, MgSiO3), forsterite (forsterite, Mg2SiO4), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), zinc (Zn), silver alloy (Ag Provided are hybrid graphene composite particles characterized by comprising a metal or semiconductor selected from the group consisting of lithium-nickel-cobalt-manganese composite oxides (NCMs), lithium-nickel-cobalt-aluminum composite oxides (NCAs), lithium-cobalt composite oxides (LCOs), lithium-nickel composite oxides (LNOs), lithium manganese oxides (LMOs), lithium iron phosphate oxides (LFPs), lithium nickel-cobalt-manganese (NCMs), and carbon powders (acetylene black, Super P black, carbon black, Denka black, activated carbon, graphite, hard carbon, soft carbon, etc.).

[0020] In addition, the graphene composite of the present invention provides hybrid graphene composite particles having a network structure formed by interconnecting the three-dimensional porous graphene structure and the primary fine particles.

[0021] In addition, the secondary fine particles of the present invention may be graphite, graphene, graphene-coated graphite, graphene-coated silicon, and silicon, silver (Ag), silicon (Si), silicon carbide (SiCX including SiC, SiC, or SiC), silicon oxide (SiOX including SiO), silicon composite oxide (Si-MgSiOx), magnesium metasilicate (enstatite, MgSiO3), forsterite (forsterite, MgSiO4), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), zinc (Zn), silver alloy (Ag Provided are hybrid graphene composite particles characterized by comprising one or more selected from the group consisting of lithium-nickel-cobalt-manganese composite oxides (NCMs), lithium-nickel-cobalt-aluminum composite oxides (NCAs), lithium-cobalt composite oxides (LCOs), lithium-nickel composite oxides (LNOs), lithium manganese oxides (LMOs), lithium iron phosphate oxides (LFPs), and lithium nickel-cobalt-manganese oxides (NCMs). [Effects of the Invention]

[0022] The anode or cathode for a lithium ion battery according to the present invention includes, as an active material, a three-dimensional porous hybrid graphene composite manufactured by a photochemical, photothermal irradiation, or heat treatment process, thereby forming a stable graphene composite structure and significantly improving charge / discharge speed and efficiency with high electrical conductivity. Furthermore, the capacity in which lithium ions can be bound can be maximized, thereby realizing a lithium ion battery with both high performance and stability. [Brief explanation of the drawings]

[0023] [Figure 1a] 1A and 1B are a scanning electron microscope (SEM) photograph and a conceptual diagram showing silver particles (Ag) before a photothermal irradiation step is carried out. [Figure 1b]1 is a scanning electron microscope (SEM) photograph showing silver particles (Ag) after a photothermal irradiation step. [Figure 1c] 1 is a scanning electron microscope (SEM) photograph showing a porous graphene structure (3D nanoporous graphene) produced by photochemical, photothermal irradiation, or heat treatment without metal particles. [Figure 1d] 1 is a scanning electron microscope (SEM) photograph of a graphite hybrid graphene composite particle according to an embodiment of the present invention, which is composed of graphite as secondary fine particles and silicon as primary fine particles. [Figure 1e] 1 is a scanning electron microscope (SEM) photograph of a graphene composite made of primary fine silicon particles and multilayer graphene, which is an example of the present invention. [Figure 1f] 1A and 1B are a conceptual diagram and an enlarged image photograph of a graphene composite of the present invention. [Figure 1g] Same as above [Figure 2] 1 is a graph showing current measurement results depending on the concentration of an electrochemically measured material (PAP) for a hybrid graphene composite electrode (Graphene-Ag electrode) for a battery active material according to the present invention, a graphene electrode, and a metal electrode (Gold electrode). [Figure 3] 1 is a graph comparing current values ​​at the same concentration (10-3 mM) of PAP for a hybrid graphene composite for a battery active material according to the present invention, graphene, and metal (Au); [Figure 4] 1 is a real-time graph showing the measurement of various concentrations of an electrochemically analyte (PAP) using a hybrid graphene composite particle electrode according to the present invention. [Figure 5]FIG. 1 is a cross-sectional schematic diagram of an example of an all-solid-state battery including the negative electrode for an all-solid-state battery according to the present invention, the all-solid-state battery including a positive electrode including a positive electrode active material (NMC), a sulfide-based solid electrolyte layer, and a negative electrode including a negative electrode current collector (SUS) and a negative electrode active material layer including a negative electrode active material made of the hybrid graphene composite. [Figure 6] 1A and 1B are photographs showing cross sections of a negative electrode for an all-solid-state battery containing the hybrid graphene composite particles of the present invention in a charged state (a) and a discharged state (b). [Figure 7] 1 is a photograph of a hybrid graphene anode (left) prepared according to the present invention and a coin cell battery (right) prepared using the same. [Figure 8] 10 is a graph showing the battery capacity as a function of the number of charge / discharge cycles when a battery anode material is made of silicon and when a battery anode material is made of silicon particles coated with hybrid graphene according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] In describing the present invention, if it is determined that a detailed description of related well-known functions or configurations may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0025] Since the embodiments of the inventive concept can be variously modified and can have various forms, specific embodiments will be illustrated in the drawings and described in detail in the specification and application, but it is not intended to limit the embodiments of the inventive concept to the specific disclosed forms, and it should be understood that all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention are included.

[0026] The terms used in this specification are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprise" or "have" are intended to specify the presence of stated features, numbers, steps, operations, components, parts, or combinations thereof, and should be understood not to preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] The present invention will be described in detail below. Within the battery's anode, graphite stores lithium in the form of LiC6 (Li+6C=LiC6), where lithium is surrounded by six carbon atoms, while silicon combines with lithium ions to form Li22Si5 (22Li+5Si=Li22Si5). While carbon can only accommodate one lithium ion for every six atoms, silicon can accommodate 22 lithium ions for every five atoms, making it far more efficient than graphite. In fact, silicon boasts excellent energy capacity of 4,200mAh / g, more than 10 times greater than graphite's 372mAh / g.

[0028] However, anode materials undergo a phenomenon known as lithiation, in which the volume of the anode increases as lithium ions are stored. While graphite expands in volume by approximately 10-20%, silicon (Si) undergoes a significant volume expansion of 4-5 times as 4.4 lithium ions react with each silicon particle to form a Li22Si5 alloy. Silicon anode active materials, in particular, are prone to crystalline cracking. As a result, repeated charge and discharge cycles can cause pulverization (particle cracking and fracture) of the silicon anode active material, resulting in electrical isolation from the current collector (Cu electrode plate), a rapid decrease in energy capacity, and a shortened battery life.

[0029] In the present invention, primary silicon particles are coated with graphene to form a hybrid graphene multilayer structure. Therefore, the expansion of silicon is efficiently suppressed, preventing cracking caused by volumetric changes in silicon. Furthermore, because the silicon particles are interconnected by multilayer graphene, the problem of weakened electrical contact between particles due to the formation of solid-electrolyte interphase (SEI) around the silicon particles is also resolved.

[0030] The hybrid graphene, in which the primary fine particles and graphene are bonded, surrounds the secondary fine particles and fills the spaces between them. This electrically connects the primary fine particles and the secondary fine particles, allowing lithium ions to efficiently bond to the primary fine particles and the secondary fine particles. This prevents the large volume change that occurs when a negative electrode is constructed using only primary silicon particles, thereby extending the battery's lifespan, and the high electrical connectivity enables faster charging and discharging.

[0031] The present invention relates to a graphene composite having a structure in which a plurality of primary fine particles and multi-layer graphene are mixed, and secondary fine particles surrounded or coated by the graphene composite, The primary fine particles are bonded to the surface or inside of the multilayer graphene, and some of the fine particles are coagulated and bonded to each other; The multilayer graphene has a three-dimensional structure in which many layers of graphene are stacked and bent in any direction, The graphene composite is produced by a photochemical, photothermal irradiation, or heat treatment process; The graphene composite is characterized in that a portion of the vacant spaces between the primary fine particles is filled and interconnected.

[0032] In this regard, graphene in the hybrid graphene composite particles has high electron mobility, thereby uniformly and smoothly supplying electrons, thereby increasing the charge / discharge speed and efficiency of the all-solid-state battery. In addition, graphene has a high Young's modulus, thereby efficiently supporting the expansion of the negative electrode active material due to the bonding of particles such as silicon (Si) particles with lithium (Li).

[0033] On the other hand, the graphene constituting the graphene composite is preferably derived from a three-dimensional porous graphene structure, rather than pure graphene without defects.

[0034] The graphene composite has a three-dimensional structure in which multiple layers of graphene are stacked and bent in any direction, the primary fine particles are bonded to the surface or inside of the graphene by photochemistry, photothermal irradiation, or heat treatment, and some fine metal particles have a structure in which they are mutually bonded and solidified, A part of the empty space between the primary fine particles is filled with the graphene composite to form an interconnected structure.

[0035] The primary fine particles may have a surface coated with graphene.

[0036] The hybrid graphene composite particle of the present invention is obtained by adding secondary fine particles to the graphene composite, and as a result, has a characteristic structure in which the graphene composite is surrounded or coated by secondary fine particles.

[0037] Pure graphene without defects has excellent physical properties such as excellent electrical conductivity and a high specific surface area, but the advantages of the increased specific surface area are significantly reduced due to irreversible self-aggregation.

[0038] In contrast, a 3D porous graphene structure in which pores are organically connected three-dimensionally between single and / or multiple graphene sheets exhibits relatively superior properties in electrochemical applications such as energy conversion and storage devices due to reduced self-aggregation, a relatively larger specific surface area, and faster diffusion of electrons and ions. Furthermore, a 3D porous graphene structure has the advantage that pore characteristics (such as pore position and size) can be controlled by controlling process variables during its manufacturing process.

[0039] Furthermore, the three-dimensional porous graphene structure can also adjust its electrical properties by changing the electronic structure of graphene through chemical doping, which adsorbs different materials such as fine particles, like the graphene-primary fine particle composite according to the present invention.

[0040] Meanwhile, methods for producing hybrid graphene composite particles are not particularly limited, but methods that utilize hard or soft templates are commonly used. Hard template methods include those that utilize spherical polymers, metal oxide particles, and porous substrates such as nickel foam. The soft template method can synthesize materials with controlled pore size using micellar templates formed by the self-assembly of surfactant molecules, and has the advantage of being relatively easy to remove the template compared to the hard template method.

[0041] Alternatively, a 3D porous graphene structure can be fabricated by forming a polymer coating layer, inducing a stabilization reaction so that carbon atoms in the polymer form a hexagonal ring arrangement, and carbonizing the polymer at high temperature. Specific examples of the polymer include, but are not limited to, poly(methyl methacrylate) (PMMA), polystyrene (PS), polyimide (PI), polyetherimide (PEI), and Kapton film. There are no particular restrictions on the structure, molecular weight, glass transition temperature, etc. of the polymer, as long as it can be carbonized at high temperature to serve as a carbon source for forming graphene.

[0042] The primary fine particles constituting the graphene composite to be combined with the graphene are silver (Ag), silicon (Si), silicon carbide (SiC, SiC, or SiC, including SiC). X ), silicon oxide (SiO or SiO containing SiO X ), silicon composite oxide (Si-Mg x SiO x), magnesium metasilicate (enstatite, MgSiO3), forsterite (forsterite, Mg2SiO4), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), zinc (Zn), silver alloy (Ag alloy), copper (Cu) coated with silver (Ag) and silver (Ag) coated with copper (Cu), lithium-nickel-cobalt-manganese composite oxide (NCM), lithium-nickel-cobalt-aluminum composite oxide (NCA), lithium-cobalt composite oxide (LCO) and lithium-nickel composite oxide (LNO), lithium manganese (LMO), lithium iron phosphate (LFP), lithium nickel-cobalt-manganese (NCM), carbon powder (acetylene black, Super P black, carbon black, Denka black, activated carbon The fine particles may be made of a metal or semiconductor selected from the group consisting of carbon, graphite, hard carbon, soft carbon, etc., and are not necessarily limited to the metal particles mentioned above.

[0043] Taking silver (Ag) particles as an example of the metal particles, silver (Ag) particles dissolve in lithium (Li) and reduce the energy required for lithium to crystallize, allowing lithium to grow more uniformly rather than unevenly due to the generation of pores, thereby ultimately contributing to improved performance of lithium-ion batteries.

[0044] In addition, the secondary fine particles may be graphite, graphene, graphene-coated graphite, graphene-coated silicon, and silicon, silver (Ag), silicon (Si), silicon carbide (Si2C, SiC, or SiC2 containing SiCX), silicon oxide (SiO or SiO2 containing SiOX), silicon composite oxide (Si-MgxSiOx), magnesium metasilicate (enstatite, MgSiO3), forsterite (forsterite, Mg2SiO4), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), zinc (Zn), silver alloy (Ag The oxides may include at least one selected from the group consisting of lithium-nickel-cobalt-manganese composite oxides (NCM), lithium-nickel-cobalt-aluminum composite oxides (NCA), lithium-cobalt composite oxides (LCO), lithium-nickel composite oxides (LNO), lithium manganese oxides (LMO), lithium iron phosphate oxides (LFP), and lithium nickel-cobalt-manganese oxides (NCM).

[0045] FIG. 1d is a scanning electron microscope (SEM) photograph of a graphite hybrid graphene composite particle according to one embodiment of the present invention, which is composed of graphite as secondary fine particles and silicon as primary fine particles.

[0046] FIG. 1e is a scanning electron microscope (SEM) photograph of a graphene composite made of primary fine silicon particles and multilayer graphene, which is an embodiment of the present invention.

[0047] The secondary fine particles are larger in size than the primary fine particles, and are mainly graphite or silicon particles, and can be substituted for graphene, which has the same size as graphite.

[0048] Graphite and silicon have similar functions as primary fine particles and can exhibit excellent electrical conductivity depending on the particle size.

[0049] As a method for preparing the hybrid graphene composite by combining graphene and metal particles, a method of uniformly mixing and combining a three-dimensional porous graphene structure and metal particles through a stirring process such as ball milling is possible. However, more preferably, a mixture of a uniform mixture of a three-dimensional porous graphene structure and metal particles is irradiated with light such as a laser or UV light, and the mixture is sintered through a heat treatment process, thereby preparing a hybrid graphene composite having a three-dimensional network structure in which interconnections between metal particles, interconnections between graphene sheets, and interconnections between metal particles and graphene sheets are organically formed.

[0050] The present invention can also be applied to all-solid-state lithium-ion batteries including a solid electrolyte layer. An all-solid-state battery including a negative electrode active material made of the hybrid graphene composite may include a positive electrode including a positive electrode current collector and a positive electrode active material layer, a solid electrolyte layer, and a negative electrode including a negative electrode current collector and a negative electrode active material layer including a negative electrode active material made of the hybrid graphene composite.

[0051] In this case, the positive electrode active material layer may include at least one positive electrode active material selected from the group consisting of lithium-nickel-cobalt-manganese composite oxides (NCM), lithium-nickel-cobalt-aluminum composite oxides (NCA), lithium-cobalt-based composite oxides (LCO), lithium-nickel-based composite oxides (LNO), lithium manganese oxides (LMO), lithium iron phosphate (LFP), lithium nickel-cobalt-manganese (NCM), and carbon powder (acetylene black, Super P black, carbon black, Denka black, activated carbon, graphite, hard carbon, soft carbon, etc.), but is not necessarily limited to the positive electrode active materials.

[0052] The type of solid electrolyte constituting the solid electrolyte layer is not particularly limited, and may include a sulfide-based solid electrolyte, and may be, for example, one or more selected from the group consisting of LiS-P2S5-LiI, LiS-P2S5-LiCl, LiS-P2S5-LiBr, LiS-P2S5-Li2O, LiS-P2S5-Li2O-LiI, LiS-SiS2, LiS-SiS2-LiI, LiS-SiS2-LiBr, LiS-SiS2-LiCl, LiS-SiS2-B2S3-LiI, LiS-SiS2-P2S5-LiI, LiS-B2S3, LiS-GeS2, and LiS-SiS2-Li3PO4.

[0053] The present invention will be described in more detail below with reference to examples. The embodiments of the present specification may be modified into various other forms, and the scope of the present specification is not to be construed as being limited to the embodiments detailed below. The examples of the present specification are provided to more completely explain the present specification to those skilled in the art.

[0054] FIG. 1a is a scanning electron microscope (SEM) photograph showing silver particles (Ag) before a photothermal irradiation step for producing a hybrid graphene composite, which is the negative electrode active material included in the negative electrode for a solid-state battery according to the present invention, is performed.

[0055] Referring to FIG. 1a, the silver (Ag) particles before photothermal irradiation have a spherical shape and a particle size of about 5 μm.

[0056] FIG. 1b is a scanning electron microscope (SEM) photograph showing silver particles (Ag) after the photothermal irradiation step.

[0057] Referring to Figure 1b, it was confirmed that the surfaces of the silver (Ag) particles were melted and bonded to adjacent particles through photothermal irradiation, and some particles were not connected, forming empty spaces.

[0058] FIG. 1c is a scanning electron microscope (SEM) photograph showing a porous graphene structure (three-dimensional nanoporous graphene) before a photothermal irradiation process is performed to produce a hybrid graphene composite, which is the negative electrode active material included in the negative electrode for a lithium ion battery according to the present invention.

[0059] Referring to FIG. 1c, it can be seen that the multilayer graphene has a three-dimensional structure that is stacked or bent.

[0060] FIG. 1d is a scanning electron microscope (SEM) photograph of a graphite hybrid graphene composite particle according to one embodiment of the present invention, which is composed of graphite as secondary fine particles and silicon as primary fine particles.

[0061] FIG. 1e is a scanning electron microscope (SEM) photograph of a graphene composite consisting of primary fine silicon particles and multilayer graphene, and is an enlarged photograph of only the graphene composite portion in FIG. 1d.

[0062] The hybrid graphene composite particle of the present invention has a structure including a graphene composite having a structure in which a plurality of primary fine particles and multilayer graphene are mixed, and secondary fine particles surrounded or coated by the graphene composite.

[0063] In Figures 1d and 1e, the primary fine particles are simultaneously bonded to the surface and interior of the graphene composite by photochemical, photothermal irradiation, or heat treatment, and at the same time, the primary fine particles are interconnected and solidified, and are located in the vacant spaces, forming a fixed structure.

[0064] In addition, the secondary fine particles may include at least one selected from the group consisting of graphite, graphene, graphene-coated graphite, graphene-coated silicon, and silicon, and in one embodiment of the present invention, graphite (FIG. 1d) and silicon (FIG. 1e) can be seen.

[0065] While conventional graphene requires complicated processes, including high-temperature processes, photochemical, photothermal irradiation, or heat treatment synthesized graphene can be synthesized relatively easily in a single step. Figures 1f and 1g are a conceptual diagram and enlarged image of the graphene composite of the present invention.

[0066] FIG. 2 is a graph showing current measurement results depending on the concentration of an electrochemically measured substance (p-Aminophenol, PAP) for a hybrid graphene composite for a battery active material (Graphene-Ag electrode), a graphene electrode, and a metal electrode (Gold electrode) according to the present invention.

[0067] For each electrode, the magnitude of the current signal increases with PAP concentration.

[0068] In addition, for the same concentration of PAP, the graphene electrode, which has advantages in terms of surface area and electron inflow and outflow compared to a metal electrode, produced a larger signal, and the hybrid-graphene composite electrode, which has lower resistance compared to a graphene electrode, produced a larger signal.

[0069] FIG. 3 is a graph comparing current values ​​at the same concentration (10-3 mM) of PAP for a hybrid graphene composite for a battery active material according to the present invention, graphene, and metal (Au).

[0070] 3 is a graph showing the difference in current signals measured for the same concentration of PAP for a hybrid graphene electrode (graphene metal composite), a metal electrode, and a graphene electrode used as an electrode for a battery active material. It can be seen that the magnitude of the signal measured for the graphene metal composite electrode at the same concentration is significantly larger than that for the reference electrode. Therefore, it can be seen that the current signal of the graphene metal composite electrode of the present invention is larger than that of the reference electrode, resulting in a larger SNR (Signal to Noise Ratio) than that of the reference electrode.

[0071] FIG. 4 is a real-time graph showing the measurement of various concentrations of an electrochemically analyte (PAP) using a hybrid graphene composite particle electrode according to the present invention.

[0072] FIG. 5 is a cross-sectional schematic diagram of an example of an all-solid-state battery including the negative electrode for an all-solid-state battery according to the present invention, which includes a positive electrode including a positive electrode active material (NMC), a sulfide-based solid electrolyte layer, and a negative electrode including a negative electrode current collector (SUS) and a negative electrode active material layer including a negative electrode active material made of the hybrid graphene composite.

[0073] FIG. 6 is a set of photographs showing cross sections of an all-solid-state battery negative electrode containing the hybrid graphene composite of the present invention in a charged state (a) and a discharged state (b).

[0074] While existing anodes have the problem of uneven lithium deposition, which creates pores and leads to dendrite deposition, the fine metal particles dissolve in lithium, lowering the energy required for lithium crystallization, allowing the lithium to grow uniformly. Graphene also prevents the lithium metal from growing and coming into direct contact with the solid electrolyte, preventing the solid electrolyte from decomposing and improving durability.

[0075] It acts as a three-dimensional host where lithium metal is deposited and as a protective layer that protects the solid electrolyte, improving durability.

[0076] Figure 7 shows the hybrid graphene anode (left) produced by the present invention and a coin cell battery (right) produced using it.

[0077] Figure 8 is a graph showing the relationship between battery capacity and the number of charge / discharge cycles for battery anode materials made from silicon and silicon particles coated with the hybrid graphene of the present invention. When made from silicon, the electrical connectivity between particles decreases due to volumetric changes in silicon and the formation of a solid electrolyte interphase (SEI), resulting in a rapid decrease in battery capacity with repeated charge / discharge cycles. In contrast, when made from graphene-coated silicon, the volumetric expansion of silicon is suppressed by the graphene, and even when an SEI forms, the electrical interconnections are maintained by the graphene, resulting in very little capacity loss. Therefore, when batteries are made using the graphene-coated silicon of the present invention, it is possible to create batteries that can significantly increase capacity and extend lifespan.

[0078] The present invention described above is not limited to the above-described embodiments and accompanying drawings, and it will be apparent to those skilled in the art to which the present invention pertains that various substitutions, modifications and changes can be made without departing from the technical spirit of the present invention.

Claims

1. The graphene composite has a structure in which a plurality of primary fine particles and multi-layer graphene are mixed, and secondary fine particles are surrounded or coated with the graphene composite, The primary fine particles are attached to the surface or the interior of the multi-layer graphene, The hybrid graphene composite particles have a structure in which the graphene composites are filled and interconnected with each other in part of the empty spaces between the primary fine particles.

2. The hybrid graphene composite particles according to claim 1 , characterized in that the surfaces of the primary or secondary fine particles are coated with graphene.

3. The hybrid graphene composite particle according to claim 1 , wherein the graphene composite is produced by a photochemical, photothermal irradiation, or heat treatment process.

4. The hybrid graphene composite particles according to claim 1 , wherein the primary fine particles are metal or semiconductor particles.

5. The hybrid graphene composite particle according to claim 1, wherein the surfaces of the primary fine particles are melted and solidified with the graphene, and the fine particles and the graphene are bonded to form a three-dimensional nanostructure.

6. The primary fine particles may be silver (Ag), silicon (Si), silicon carbide (SiCX including SiC, SiC, or SiC), silicon oxide (SiOX including SiO or SiO), silicon composite oxide (Si-MgSiOx), magnesium metasilicate (enstatite, MgSiO3), forsterite (forsterite, MgSiO4), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), zinc (Zn), silver alloy (Ag 2. The hybrid graphene composite particle according to claim 1, wherein the hybrid graphene composite particle is made of a metal or a semiconductor selected from the group consisting of: lithium-nickel-cobalt-manganese composite oxides (NCMs), lithium-nickel-cobalt-aluminum composite oxides (NCAs), lithium-cobalt composite oxides (LCOs), lithium-nickel composite oxides (LNOs), lithium manganese oxides (LMOs), lithium iron phosphate oxides (LFPs), lithium nickel-cobalt-manganese oxides (NCMs), and carbon powders (acetylene black, Super P black, carbon black, Denka black, activated carbon, graphite, hard carbon, soft carbon, or the like).

7. 2. The hybrid graphene composite particle of claim 1, wherein the graphene composite has a network structure formed by interconnecting the three-dimensional porous graphene structure and the primary fine particles.

8. The secondary fine particles are Graphite (Graphite), graphene, graphene-coated graphite, graphene-coated silicon, and silicon, silver (Ag), silicon (Si), silicon carbide (SiCX including SiC, SiC, or SiC), silicon oxide (SiOX including SiO), silicon composite oxide (Si-MgSiOx), magnesium metasilicate (enstatite, MgSiO3), forsterite (forsterite, MgSiO4), gold (Au), platinum (Pt), palladium (Pd), aluminum (Al), zinc (Zn), silver alloy (Ag alloy), copper (Cu) surface-coated with silver (Ag), silver (Ag) surface-coated with copper (Cu), lithium-nickel-cobalt-manganese composite oxide (NCM), lithium-nickel-cobalt-aluminum composite oxide (NCA), lithium-cobalt composite oxide (LCO), lithium-nickel composite oxide (LNO), lithium manganese (LMO), lithium iron phosphate (LFP), lithium nickel-cobalt-manganese (NCM), carbon powder (acetylene black, Super P black, carbon black, Denka black, activated carbon), hard carbon, soft carbon, etc.

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