Grafted copolymer-based liquid metal nanoparticles, binders, and batteries

Abstract

A grafted copolymer-based liquid metal nanoparticle, binder, and battery are disclosed. The liquid metal nanoparticle may comprise a droplet nanoparticle containing a liquid metal; and an ionomer-grafted copolymer coated on the surface of the droplet nanoparticle.

Description

Technology Field

[0001] The present invention relates to grafted copolymer-based liquid metal nanoparticles, a binder, and a battery. Background Technology

[0002] The commercialization of wearable electronic devices and electric vehicles is exponentially increasing the demand for high-power density energy storage systems, particularly those capable of deformation and self-healing properties. Consequently, lithium-ion batteries (LIBs) with high capacity, low internal resistance, and excellent Coulomb efficiency are being actively developed. Silicon and graphite have been widely used as anode materials for LIBs. However, while silicon possesses a high capacity, reaching a theoretical capacity of 4,200 mAh / g, it presents a problem where the electrode expands during the charging and discharging process, causing instability and deformation of the solid electrolyte interface and reducing battery performance. On the other hand, graphite is relatively stable but its theoretical capacity is limited to 372 mAh / g, and neither silicon nor graphite-based anodes exhibit deformation or self-healing properties.

[0003] In contrast, gallium-based liquid metals that remain in a liquid state at room temperature and possess a theoretical capacity of 770 mAh / g are attracting attention as self-healing cathode materials. For example, liquid metals such as eutectic gallium-indium (EGaIn) alloys exhibit excellent charge-discharge efficiency due to reversible reactions and redox reactions with lithium ions. Furthermore, the characteristic of maintaining a liquid state at room temperature can aid in the self-healing of cracks that may occur during the charge-discharge process. However, the cathode-solid electrolyte interface of EGaIn electrodes can become deformed and unstable due to volume expansion during the charge-discharge process, which can lead to performance degradation and a shortened battery life. To address this, EGaIn must be structurally stabilized within a rigid binder matrix in the form of fine or nanoparticles instead of large volumes of liquid metal. However, suppressing the re-aggregation of EGaIn nanoparticles, which have very high surface energy at room temperature, and maintaining their stability remains a major challenge that needs to be solved.

[0004] To address these issues, techniques for coating liquid metal nanoparticles with binder materials, such as conductive polymers, have been explored. Previous studies have attempted to stabilize EGaIn nanoparticles through polymer coating, but the performance and stability within LIBs have not been satisfactory; therefore, a more efficient and proactive approach is required for the development of high-performance LIBs utilizing binder-stabilized EGaIn particles.

[0005] To structurally stabilize EGaIn nanoparticles while expanding the contact area with lithium ions, it is important to use a minimal amount of binder. Additionally, binders that facilitate contact between lithium ions and the EGaIn surface by forming self-assembled molecular channels can be useful. Recently, the authors demonstrated a high-performance LIB anode in which transition metal dichalcosenide (MoS2) nanosheets were stabilized using an ionomer-grafted polymer coating. It was reported that sulfonic acid groups within the graft polymer stabilizing the MoS2 nanosheets act as lithium ion channels, thereby improving anode performance. This strategy is also applicable to EGaIn-based anodes, and devices with high performance and self-healing properties can be developed by effectively stabilizing EGaIn nanoparticles using graft copolymers.

[0006] In this invention, a novel self-healing anode based on EGaIn nanoparticles (EGaIn@GP) stabilized by an ionomer-grafted fluorinated polymer was developed to improve the stability and rate characteristics of a LIB. EGaIn nanoparticles with a size of approximately 200 nm were effectively dispersed and stabilized within the graft copolymer, thereby suppressing the re-aggregation of nanoparticles within the composite. Through systematic research, it was confirmed that ion channels formed by the self-assembled ionomer on the surface of the EGaIn nanoparticles promote the migration of lithium ions from the electrolyte to the EGaIn surface, enabling efficient electrochemical reduction of lithium ions at the nanoparticle surface. A LIB containing the EGaIn nanoparticle anode stabilized by the self-healing graft copolymer maintained 85% stability (0.5 A / g) even after 500 charge-discharge cycles, and exhibited high rate characteristics (45.1% at 2.0 A / g) and cell capacity (803.7 mAh / g at 0.1 A / g). The self-assembly strategy of EGaIn and graft copolymers can provide a universal method for designing flexible and self-healing electrodes suitable for various energy storage applications. The problem to be solved

[0007] The problem that the present invention aims to solve is to mitigate the aggregation phenomenon and electrochemical performance degradation that occur in existing technologies due to insufficient stability of liquid metal nanoparticles. means of solving the problem

[0008] In one aspect, the present invention provides a liquid metal-based nanoparticle comprising: a droplet nanoparticle containing a liquid metal; and an ionomer-grafted copolymer coated on the surface of the droplet nanoparticle.

[0009] In one embodiment, the liquid metal may include a eutectic alloy of gallium and indium (EGaIn).

[0010] In one embodiment, the ionomer may include sulfonated polystyrene (SPS) functionalized with sulfonic acid groups.

[0011] In one embodiment, the copolymer may be a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE).

[0012] In one embodiment, the ionomer grafted onto the copolymer may include sulfonated polystyrene (SPS) functionalized with sulfonic acid groups.

[0013] In one embodiment, the ratio of the ionomer grafted into the copolymer may be about 5 to 15%.

[0014] In one embodiment, the ratio of the ionomer grafted into the copolymer may be about 9 to 10%.

[0015] In one embodiment, the size of the nanoparticles may be about 50 to 200 nm.

[0016] In one embodiment, the coating may have a thickness of about 3 to 4 nm.

[0017] In one embodiment, the trifluoroethylene (TrFE) in the copolymer may be about 20 to 30 mol%.

[0018] In one embodiment, the polystyrene (SPS) functionalized with sulfonic acid groups can form a negative surface charge to inhibit the re-aggregation of nanoparticles.

[0019] In one embodiment, the liquid metal-based nanoparticles can maintain dispersion stability even after more than 500 charge-discharge cycles.

[0020] In another aspect, the present invention provides a method for manufacturing liquid metal-based nanoparticles, comprising a dispersion step of dispersing a liquid metal in a solution containing a copolymer grafted with an ionomer; wherein, in the dispersion step, the copolymer is coated on the surface of a droplet nanoparticle containing the liquid metal.

[0021] In one embodiment, the dispersion can be performed by ultrasonic dispersion.

[0022] In one embodiment, the ultrasonic dispersion can be performed at about 20 to 40 kHz.

[0023] In one embodiment, the liquid metal may include a eutectic alloy of gallium and indium (EGaIn).

[0024] In one embodiment, the ionomer may include sulfonated polystyrene (SPS) functionalized with sulfonic acid groups.

[0025] In one embodiment, the copolymer may be a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE).

[0026] In one embodiment, the ionomer grafted onto the copolymer may include sulfonated polystyrene (SPS) functionalized with sulfonic acid groups.

[0027] In one embodiment, the ratio of the ionomer grafted into the copolymer may be about 5 to 15%.

[0028] In one embodiment, the ratio of the ionomer grafted into the copolymer may be about 9 to 10%.

[0029] In one embodiment, the trifluoroethylene (TrFE) in the copolymer may be 20 to 30 mol%.

[0030] In one embodiment, the solvent of the solution may include DMSO or NMP.

[0031] In another aspect, the present invention provides a binder for an electrochemical reaction electrode comprising liquid metal-based nanoparticles, comprising: droplet nanoparticles comprising a liquid metal; and a copolymer grafted with an ionomer coated on the surface of the droplet nanoparticles.

[0032] In one embodiment, the liquid metal comprises a eutectic alloy of gallium and indium (EGaIn), the ionomer comprises sulfonated polystyrene (SPS) functionalized with sulfonic acid groups, the copolymer comprises a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE), and the grafted ratio of the ionomer in the copolymer may be about 9 to 10%.

[0033] In one embodiment, the binder can improve the electrochemical adhesion of the electrode and / or suppress the occurrence of cracks within the electrode.

[0034] In another aspect, the present invention provides an electrode for an electrochemical reaction, comprising: a binder for an electrochemical reaction electrode according to an embodiment of the present invention described above; a conductive material mixed with said binder; and a conductive substrate having said binder and said conductive material formed on its surface.

[0035] In one embodiment, the conductive material may include at least one of carbon black, carbon nanotubes (CNT), graphite, or graphene.

[0036] In one embodiment, the conductive substrate may include aluminum (Al), copper (Cu), or nickel (Ni).

[0037] In one embodiment, the binder or the conductive material may be formed on the conductive substrate by spin coating.

[0038] Research on the use of gallium-indium eutectic alloy (EGaIn) as anodes for lithium-ion batteries (LIBs) has been extensive due to its shape-deformability and self-healing properties. However, to limit damage to EGaIn anodes caused by volume expansion during lithiation and delithiation processes, chemical modification is required to stabilize the liquid metal into nanoparticles. This invention proposes a novel self-healing liquid metal anode comprising ionomer-grafted polymer ion channels to improve the stability and rate characteristics of LIBs. The ionomer-grafted fluorine-based polymer binder effectively inhibits the aggregation of the liquid metal, thereby stabilizing the liquid metal nanoparticles. Furthermore, the fluorine-based polymer binder provides ion channels that facilitate the migration of lithium ions from the electrolyte to the surface of the liquid metal nanoparticles. The efficient electrochemical reduction reaction of lithium ions on these surfaces enables high-performance LIBs, which is demonstrated by improved stability (85% retention rate after 500 cycles, under 0.5 A / g conditions), rate characteristics (45.1% under 2.0 A / g conditions), and cell capacity (803.7 mAh / g under 0.1 A / g conditions). The cathode containing a copolymer grafted to stabilize liquid metal nanoparticles can be mass-produced through a simple solution process and can provide a new strategy for the development of high-performance liquid metal-based LIBs. Effects of the invention

[0039] The effect of the present invention is to contribute to the long-term maintenance of electrochemical performance by suppressing the re-aggregation of liquid metal nanoparticles and improving dispersion stability. In addition, by enabling the formation of ion channels through an ionomer grafted onto a copolymer, it can improve the mobility of lithium ions and help the electrode operate efficiently. Brief explanation of the drawing

[0040] FIG. 1 illustrates one form of a liquid metal-based nanoparticle according to an embodiment of the present invention. FIG. 2 illustrates a method for manufacturing liquid metal-based nanoparticles according to an embodiment of the present invention. Fig. 3. Characterization and dispersion of EGaIn@GP in a lithium-ion half-cell (LIB). a) Schematic of a lithium-ion half-cell including an EGaIn@GP cathode. Shows the movement of lithium ions and electrons during the charging and discharging process. b) Schematic illustrating the mechanism by which PVDF-TrFE-g-SPS binder enhances lithium ion diffusion at the cathode. c) 1H-nuclear magnetic resonance (NMR) spectra of PVDF-TrFE (black) and PVDF-TrFE-g-SPS (red). Confirms successful grafting. d) Schematic showing the EGaIn@GP suspension solution. e) Change in absorption coefficient of EGaIn@GP according to different graft polymer concentrations. f) Photograph of the dispersed solution. g) Ultraviolet-visible (UV-vis) absorption spectrum. h) Change in absorption rate over time. i) Measurement of zeta potentials of EGaIn, EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) suspensions. Fig. 4. Characterization and structural analysis of the solid-state EGaIn@GP cathode. a) Particle size distribution of EGaIn and EGaIn@GP. b) TEM images and energy dispersive spectral (EDS) maps of fluorine in EGaIn and EGaIn@GP. c) Phase TEM image of EGaIn@GP nanoparticles. d) Cross-sectional scanning electron microscope (SEM) image of EGaIn@GP formed on a copper current collector. e) C 1s XPS spectrum of a thin EGaIn@GP film. Shows chemical composition. f) FT-IR patterns of GP and EGaIn@GP. g) XRD patterns of PVDF-TrFE(P), PVDF-TrFE-g-SPS(GP), EGaIn, EGaIn@P, and EGaIn@GP. Fig. 5. Evaluation of adhesion and self-healing properties of EGaIn@GP cathode. a) Schematic illustrating the adhesion test process for attaching and detaching EGaIn@GP to a copper current collector. b) Percentage of weight change after multiple bonding cycles for various compositions (EGaIn, EGaIn@P, EGaIn@GP(50%), EGaIn@GP(100%)). c) Schematic illustrating the self-healing process of EGaIn@GP, which promotes the redistribution and recombination of nanoparticles on a copper current collector using DMSO. d) Change in resistance of various EGaIn@GP cathode samples after self-healing. Fig. 6. Electrochemical characteristics of a LIB half-cell including an EGaIn@GP cathode-based electrode. a) Schematic of the EGaIn@GP electrode. It shows the lithiation process during battery operation. b) dQ / dV plot of a LIB half-cell containing a graft copolymer cathode (current rate 0.5 A / g). c) Charge / discharge voltage profile of a LIB half-cell containing an EGaIn@GP cathode. d) Comparison of rate performance of LIB half-cells including a cathode composed of EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%). Fig. 7. Analysis of cycle performance of a LIB half-cell including an EGaIn@GP cathode. a) Cycle performance and Coulomb efficiency (current rate 0.5 A / g) of a LIB half-cell including an EGaIn@GP cathode. b) Comparison of cycle performance of LIB half-cells including EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) cathodes (current rate 1.0 A / g). c) Electrochemical impedance spectroscopic (EIS) curves of LIB half-cells including EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) cathodes. d) Impedance (Z') and w-1 / 2 plots of LIB half-cells including EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) cathodes. e) Schematic illustrating a self-healing cathode highlighting the difference between EGaIn and EGaIn@GP during the lithiation and delithiation processes. f) SEM images of the initial state (left) and after cycling (right) of the EGaIn@GP cathode. Specific details for implementing the invention

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. Similar reference numerals have been used for similar components in the description of each drawing. In the attached drawings, the dimensions of the structures are shown enlarged compared to the actual dimensions for the clarity of the present invention.

[0042] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “comprising” or “having” are intended to specify the presence of the features, numbers, steps, actions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, or combinations thereof. In the context of this specification, terms such as “about” may mean about ± 1%, about ± 2%, about ± 3%, about ± 4%, about ± 5%, about ± 6%, about ± 7%, about ± 8%, about ± 9%, or about ± 10% of the figures described in the specification.

[0043] In addition, the description of one aspect of the present invention may be applied identically or similarly to the description of other aspects for identical or similar configurations or terms.

[0044] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0045] FIG. 1 illustrates one form of a liquid metal-based nanoparticle (100) according to an embodiment of the present invention. Referring to FIG. 1, the liquid metal-based nanoparticle (100) according to an embodiment of the present invention may include a droplet nanoparticle (110) containing a liquid metal; and an ionomer-grafted copolymer (120) coated on the surface of the droplet nanoparticle (110).

[0046] In the context of this specification, the term "nanoparticle" refers to a material having a particle size in the nanometer range, wherein its physical properties or chemical reactions are uniquely determined by the particle size. In particular, the nanoparticles used in this invention consist of a liquid metal as a core component and have a structure with enhanced stability through a copolymer coating.

[0047] In the context of this specification, the term droplet refers to a substance in a liquid state that is separated into fine particle forms and has an independent spherical or quasi-spherical shape.

[0048] In the context of this specification, the term "liquid metal" refers to a material that maintains a liquid state at room temperature or a near-room temperature and possesses the inherent conductivity and fluidity of a metal. Such materials provide structural stability by forming a surface oxide film and, when processed into nanoparticle form, can exhibit unique physical and electrochemical properties distinct from solid metals.

[0049] The type of liquid metal is not particularly limited. In one embodiment, the liquid metal may include a eutectic alloy of gallium and indium (EGaIn). The eutectic alloy of gallium and indium (EGaIn) is a mixture that forms a melting point at about 15.7 °C and can provide excellent electrical and thermal conductivity.

[0050] Non-limiting examples of other possible liquid metal types include pure gallium, indium, bismuth, tin, or their alloys. For example, gallium-tin alloys (GaSn) or gallium-bismuth alloys (GaBi) can provide low melting points and electrochemical stability, respectively, making them suitable for specific applications. These liquid metals can be considered candidates that can open up various possibilities in electrochemical reactions, thermal conductivity applications, or nanoparticle technology.

[0051] In the context of this specification, the term "coating" refers to a process of forming a thin, uniform layer on the surface of a material to protect it or impart functionality. In the present invention, a copolymer is chemically and physically bonded to the surface of liquid metal nanoparticles to form a coating layer. This coating can help adjust the surface charge of the nanoparticles, prevent re-aggregation, and provide a pathway for the movement of lithium ions.

[0052] In the context of this specification, the term "ionomer" refers to a polymer containing ionic functional groups within its polymer chains. This enables the induction of surface charge and ion channel formation in nanoparticles.

[0053] The material of the ionomer is not particularly limited. In one embodiment, the ionomer may include sulfonated polystyrene (SPS). SPS contains sulfonate groups (-SO3H) to impart a negative charge to its surface, which can help suppress the re-aggregation of nanoparticles and improve dispersion stability. Additionally, it has the potential to improve electrochemical reaction efficiency by enhancing ion conductivity.

[0054] Non-limiting examples of other ionomer materials include sulfonated polyimide (SPI), polyetheretherketone (SPEEK), polyphenylene oxide (SPPO), polybenzimidazole (SPBI), polyethylene (SPE), polytetrafluoroethylene (SPTFE), polystyrene-polybutadiene (SPS-PB), polysulfone (SPSf), nylon (SNylon), polyvinyl alcohol (SPVA), polyurethane (SPU), polyacrylonitrile (SPAN), polymethyl methacrylate (SPMMA), polyisoprene (SPIso), polycarbonate (SPC), polyvinyl chloride (SPVC), polyterephthalate (SPET), polylactic acid (SPLA), polycaprolactone (SPCL), polyester (SPEst), polybutadiene (SPB), and acrylate-based copolymers. Polyetheretherketoneketone (PEEK-K), polyetherimide (PEI), polyethersulfone (PES), fluoropolymer (SFP), polymer electrolyte membrane (PEM), polysiloxane, polyphenylene sulfide (PPS), and ion exchange resin are available. These ionomers have the potential to improve ion conductivity, dispersion stability, and durability depending on their respective chemical and physical properties, and can be used in various electrochemical and materials applications.

[0055] In the context of this specification, the term "graft" refers to the process of chemically bonding a side-chain polymer to a main-chain polymer. In the context of this specification, the term "copolymer" refers to a polymer composed of two or more monomers, each monomer may provide unique physical or chemical properties.

[0056] In one embodiment, the copolymer may be a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE). Polyvinylidene fluoride (PVDF) is a fluorine-based polymer with high chemical stability and mechanical strength, which can provide excellent durability and thermal stability. Additionally, PVDF has the potential to contribute to enhancing electrical performance in electrochemical environments through its polarization properties. Trifluoroethylene (TrFE) is a monomer with a high fluorine content, which can increase flexibility and polarity when copolymerized with PVDF. TrFE maintains stability even under electrochemical reaction conditions and can help improve the electrical performance of the material by enhancing dielectric properties.

[0057] Non-limiting examples of other possible polymers / copolymers include polyetheretherketone (PEEK), polyimide (PI), polybenzimidazole (PBI), polyethylene (PE), polycarbonate (PC), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polysulfone (PSU), polyphenylene oxide (PPO), polyester (PET), polylactic acid (PLA), polycaprolactone (PCL), polybutadiene (PBD), polyurethane (PU), polymethyl methacrylate (PMMA), polyisoprene (PIso), acrylate-based copolymers, polyethersulfone (PES), polyterephthalate (PET), polyvinyl chloride (PVC), polysiloxane, polyphenylene sulfide (PPS), polymer electrolyte membranes (PEM), polymer blends, and synthesized functional copolymers.

[0058] In one embodiment, the ratio of the ionomer grafted into the copolymer may be about 5 to 15%. In one embodiment, the ratio of the ionomer grafted into the copolymer may be about 9 to 10%.

[0059] In the context of this specification, the term “grafted ratio” refers to the ratio of ionomer actually grafted onto the copolymer main chain, which describes how much ionomer is chemically bonded relative to the total number of graftable sites on the copolymer main chain. For example, when there are 100 possible bonding sites on the copolymer main chain, a 10% grafting ratio means that ionomer is bonded to 10 of those sites. This ratio can have a significant impact on the physical and chemical properties, electrochemical performance, and dispersion stability of the copolymer.

[0060] If the graft ratio is excessively low, the ionomer concentration may be insufficient, preventing the ionic properties of the copolymer from being fully expressed. This may result in insufficient negative charge formation on the nanoparticle surface or limited ion channel generation, potentially reducing electrochemical efficiency. Additionally, if there is insufficient ionomer bonding, the functional versatility of the copolymer may decrease, and the electrostatic repulsion required to ensure the dispersion stability of the nanoparticles may not be sufficiently provided. If the graft ratio is excessively high, the structural flexibility of the copolymer may be reduced, potentially damaging its physical properties. Excessive ionomer bonding can weaken the mechanical strength of the copolymer main chain and cause the coating layer of the nanoparticles to become excessively thick. Consequently, there is a risk that ion transport pathways in electrochemical reactions may be obstructed or the durability of the material may decrease.

[0061] In one embodiment, the size of the nanoparticles may be about 50 to 200 nm. If the size of the nanoparticles is excessively small, the surface area increases excessively, which may intensify aggregation between the nanoparticles. This reduces the effective stabilization ability of the copolymer coated on the particle surface, thereby impairing dispersion stability and potentially causing aggregated particles to reduce efficiency in electrochemical reactions. Additionally, if the size is too small, the thickness and uniformity of the copolymer coating may not be ensured, which may limit the protective and functional role of the nanoparticle surface. If the size of the nanoparticles is excessively large, the surface area per unit volume decreases, which may result in a reduction of the surface active area in electrochemical reactions. This may reduce the mobility and reaction efficiency of lithium ions and increase the likelihood of decreased electrochemical performance in high current density environments. Furthermore, large nanoparticles are difficult to uniformly coat and disperse during the manufacturing process, and it is difficult to achieve a uniform distribution within the electrode, which may lead to a decrease in the physical stability of the electrode.

[0062] In one embodiment, the coating may have a thickness of about 3 to 4 nm. In one embodiment, the coating may have a thickness of about 3.4 nm. If the coating is excessively thin, there is a possibility that the surface protection function of the liquid metal nanoparticles may not be sufficiently expressed. A thin coating may not effectively stabilize the oxide film on the surface of the nanoparticles, which may lead to aggregation and reduced dispersion stability. Furthermore, if the uniformity of the coating layer is not ensured, the surface charge distribution of the nanoparticles may become non-uniform, potentially causing variability in electrochemical performance. If the coating is excessively thick, the surface active area of ​​the nanoparticles may decrease, potentially leading to reduced efficiency in electrochemical reactions. A thick coating may increase ion transport pathways and result in reduced conductivity within the electrode. Additionally, excessive coating may increase the volume ratio of the electrode material, potentially lowering the energy density of the battery.

[0063] In one embodiment, the trifluoroethylene (TrFE) in the copolymer may be about 20 to 30 mol%. If the proportion of polyvinylidene fluoride (PVDF) in the copolymer is excessively high, the crystallinity of the copolymer may increase, potentially leading to a decrease in flexibility and polarization properties. While PVDF provides high strength and durability, if the proportion of TrFE is low, ionic conductivity and dielectric properties may not be sufficiently expressed. Additionally, if the proportion of PVDF increases, the copolymer may become relatively rigid, potentially reducing electrical adhesion. If the proportion of trifluoroethylene (TrFE) in the copolymer is excessively high, the structural stability of the copolymer may decrease, potentially weakening physical strength and durability. Although TrFE plays a role in increasing polarity, if the proportion becomes excessively high, the mechanical properties of the copolymer become unbalanced, which may lead to reduced thermal and chemical stability in an electrochemical environment.

[0064] In one embodiment, the polystyrene (SPS) functionalized with sulfonic acid groups can suppress the re-aggregation of nanoparticles by forming a negative surface charge. This principle is possible because the negative charge of the sulfonic acid groups induces electrostatic repulsion between nanoparticles. The negative surface charge helps the nanoparticles disperse uniformly within the electrolyte and contributes to enhancing stability. In particular, such stability can help the nanoparticles remain independent even under conditions where aggregation may intensify, such as at high current densities.

[0065] In one embodiment, the liquid metal-based nanoparticles (100) can maintain dispersion stability even after more than 500 charge-discharge cycles. This effect may be attributed to the uniformity and durability of the copolymer coating layer. The copolymer may stably bind to the surface of the nanoparticles to prevent physical damage and minimize surface changes caused by chemical reactions. Additionally, a coating functionalized with sulfonic acid groups can help maintain electrical contact while suppressing the formation of an oxide film on the surface of the nanoparticles. This limits structural changes in the nanoparticles under battery charge-discharge conditions and can have a positive effect on increasing the performance retention rate within the electrode.

[0066] The advantage of the liquid metal-based nanoparticles (100) according to the embodiment of the present invention described above is that uniform performance and a long lifespan can be expected in various electrochemical applications. The design of the nanoparticles can enhance dispersion stability and optimize electrical properties, thereby opening up the possibility of utilizing them as a negative electrode material for high-efficiency lithium-ion batteries. In particular, they have the characteristic of being able to suppress the degradation of electrode performance even under demanding conditions such as high current density.

[0067] FIG. 2 illustrates a method (200) for manufacturing liquid metal-based nanoparticles according to an embodiment of the present invention. Referring to FIG. 2, the method (200) for manufacturing liquid metal-based nanoparticles according to an embodiment of the present invention may include a dispersion step (S210) of dispersing a liquid metal in a solution containing a copolymer grafted with an ionomer.

[0068] In one embodiment, the copolymer may be coated on the surface of the liquid metal-containing droplet nanoparticles during the dispersion step (S210). This may enable the liquid metal nanoparticles to form a structure that prevents re-aggregation while maintaining dispersion stability. The copolymer coating provides a uniform protective layer on the surface of the nanoparticles and can help maintain ion conductivity in an electrochemical reaction environment.

[0069] In one embodiment, the dispersion can be performed by ultrasonic dispersion. The advantage of ultrasonic dispersion is that it uniformly disperses nanoparticles to prevent aggregation and provides the possibility of ensuring the uniformity of the copolymer coating layer. Ultrasound transmits fine vibrations to liquid metal nanoparticles to effectively separate the particles and helps maintain a stable dispersion state within the solution.

[0070] In one embodiment, the ultrasonic dispersion can be performed at approximately 20 to 40 kHz. If the frequency is excessively low, there is a possibility that the dispersion effect of the liquid metal nanoparticles may be limited due to insufficient ultrasonic energy. In this case, the uniformity of the coating layer may not be ensured because the aggregated nanoparticles are not sufficiently separated. If the frequency is excessively high, there is a risk that the copolymer and the liquid metal nanoparticles may be damaged due to excessive energy generated by the ultrasound. High frequencies can apply excessive stress to the particle surface, increasing the likelihood that the size and shape of the nanoparticles may be deformed.

[0071] Non-limiting examples of other dispersion methods are as follows. High-speed stirring disperses particles through powerful mechanical rotation within a solution and can be applied with simple equipment, but may have limitations when highly stable dispersion is required. Ball milling physically grinds and disperses particles and can be useful in mass production environments. Jet milling disperses particles using high-speed gas flow and allows for fine particle size control. Supercritical fluid dispersion uses a supercritical fluid to uniformly disperse particles, enabling nano-level control. Mechanical homogenization is a method of uniformly mixing particles within a solution by applying high pressure. Spray drying disperses particles by spraying liquid metal into a solution and may be suitable for processes requiring rapid drying. Electric field dispersion achieves a dispersion effect by utilizing an electric field to increase repulsive forces between particles. Fluidized bed dispersion maintains a dispersed state by flowing particles together with a gas or liquid. Coraloid milling evenly mixes particles using rotational force and pressure, which can enhance dispersibility and uniformity. High-pressure homogenization is a method that refines particles and disperses them uniformly through high pressure. Magnetic stirring is a method that disperses particles by generating mixing forces within a solution using magnets. Centrifugation utilizes centrifugal force to induce separation and dispersion based on particle size. Gas-induced mixing is a method that effectively mixes liquids and particles by injecting gas at high speeds. Chemical stabilization involves adding surfactants to suppress particle aggregation and enhance dispersion. Vertical stirring is a method that uniformly disperses particles and a solution by mixing them through stirring in a specific direction. Impact dispersion disperses aggregated particles through physical impact and is particularly suitable for high-viscosity solutions. Acoustic fluid mixing is a method that mixes particles and a solution using sound energy, which can be advantageous for non-contact dispersion.Vacuum mixing disperses particles under vacuum conditions to minimize air bubbles and maximize the dispersion effect. Surfactant dispersion is a method that maintains particle stability and dispersion by controlling interfacial tension. Mechanical shear mixing disperses particles by applying high-speed shear force and can be particularly effective in high-viscosity systems. These various dispersion methods can be selectively applied based on their respective advantages and disadvantages.

[0072] In one embodiment, the liquid metal may comprise a eutectic alloy of gallium and indium (EGaIn). In one embodiment, the ionomer may comprise sulfonated polystyrene (SPS) functionalized with sulfonic acid groups. In one embodiment, the copolymer may be a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE). In one embodiment, the ionomer grafted onto the copolymer may comprise sulfonated polystyrene (SPS) functionalized with sulfonic acid groups. In one embodiment, the proportion of the ionomer grafted onto the copolymer may be about 5 to 15%. In one embodiment, the proportion of the ionomer grafted onto the copolymer may be about 9 to 10%. In one embodiment, the trifluoroethylene (TrFE) in the copolymer may be 20 to 30 mol%.

[0073] In one embodiment, the solvent of the solution may include dimethyl sulfoxide (DMSO) or N-methyl-2-pyrrolidone (NMP). The advantage of DMSO is that it has high polarity and provides excellent solvent performance capable of dissolving various organic compounds. Additionally, DMSO has low viscosity, which facilitates mixing and dispersion during the process and helps maintain the uniformity of the solution. The advantage of NMP is that it can maintain high thermal stability over a wide temperature range. Furthermore, as a polar solvent, NMP has high compatibility with copolymers and various polymeric materials and can induce uniform dispersion of nanoparticles during the process. NMP has a low vapor pressure, resulting in minimal volatile loss, and allows for easy recovery of residual solvent even after the process.

[0074] The advantage of the manufacturing method (200) according to the embodiment of the present invention is that liquid metal nanoparticles can be uniformly dispersed and a copolymer can be stably coated on the surface of the nanoparticles. This process can help maximize the dispersion stability of the nanoparticles and prevent re-aggregation by utilizing an ionomer-grafted copolymer. In addition, by introducing precise dispersion techniques such as ultrasonic dispersion, the size of the nanoparticles and the coating thickness can be uniformly controlled, which may improve electrochemical performance. This manufacturing method can increase process efficiency and enable mass production of high-performance materials that can be used in various application fields.

[0075] Meanwhile, a binder for an electrochemical reaction electrode according to an embodiment of the present invention may include liquid metal-based nanoparticles comprising: droplet nanoparticles containing a liquid metal; and a copolymer grafted with an ionomer coated on the surface of the droplet nanoparticles.

[0076] In the context of this specification, the term "binder" refers to a substance that serves to help ensure stable electrochemical reactions by binding or fixing electrode materials. The binder provides adhesion between electrode components, such as conductive materials, electrolytes, and nanoparticles, and can help maintain physical and chemical stability in an electrochemical reaction environment.

[0077] By including the liquid metal-based nanoparticles in the binder, dispersion stability within the electrode can be maximized, and the nanoparticles can be prevented from re-aggregating even during electrochemical reactions. In particular, the uniform distribution of nanoparticles can help optimize the lithium ion migration pathway and reduce the electrical contact resistance of the electrode.

[0078] In one embodiment, the liquid metal comprises a eutectic alloy of gallium and indium (EGaIn), the ionomer comprises sulfonated polystyrene (SPS) functionalized with sulfonic acid groups, the copolymer comprises a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE), and the grafted ratio of the ionomer in the copolymer may be about 9 to 10%.

[0079] In one embodiment, the binder can improve the electrochemical adhesion of the electrode and / or suppress the occurrence of cracks within the electrode. This maintains a stable bond between the electrode material and the current collector, thereby potentially preventing detachment of the material or structural damage during the charging and discharging process. Additionally, the uniform distribution of the binder can help relieve internal stress in the electrode, thereby helping to suppress mechanical deformation or cracks that may occur during the charging and discharging process.

[0080] An advantage of the binder according to the embodiment of the present invention is that it can simultaneously provide high conductivity and dispersion stability by including liquid metal-based nanoparticles. This makes it possible to minimize the degradation of electrode performance in an electrochemical reaction environment and maintain long-term reliability. In addition, the ionomer-grafted copolymer can help improve the mobility of lithium ions by imparting ion conductivity within the binder.

[0081] Meanwhile, an electrode for an electrochemical reaction according to an embodiment of the present invention may comprise: a binder for an electrochemical reaction electrode according to the embodiment of the present invention described above; a conductive material mixed together with said binder; and a conductive substrate having said binder and said conductive material formed on its surface.

[0082] The role of the aforementioned conductive material is to ensure electrical conductivity within the electrode to effectively support electrochemical reactions. Such materials can enhance the overall performance of the electrode by strengthening electrical connectivity between electrode components and rapidly transferring charges generated during the reaction. Furthermore, the conductive material can contribute not only to electrical conductivity but also to increased durability by reinforcing the physical structure of the electrode.

[0083] In one embodiment, the conductive material may include at least one of carbon black, carbon nanotubes (CNT), graphite, or graphene. Other non-limiting examples of the conductive material include acetylene black, uncalcined carbon, activated carbon, polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh), silver nanowires, gold nanoparticles, nickel nanoparticles, aluminum-plated particles, conductive polymers, carbon nanofibers (CNF), conductive nanoplates, vanadium oxide, titanium dioxide (TiO2), indium tin oxide (ITO), conductive organic nanostructures, vanadium oxide nanotubes, and silicon-based conductive nanostructures.

[0084] The role of the conductive substrate is to serve as a physical support for the electrode and, at the same time, to provide an electron transport path to support the smooth progress of electrochemical reactions. The conductive substrate acts as a medium connecting the electrode and the external circuit, stably fixes the electrode components, and can maintain long-term electrical contact.

[0085] In one embodiment, the conductive substrate may comprise aluminum (Al), copper (Cu), or nickel (Ni). Other non-limiting examples of the conductive substrate include gold (Au), silver (Ag), platinum (Pt), stainless steel, iridium, titanium (Ti), molybdenum (Mo), tantalum (Ta), graphite sheet, conductive ceramic, doped silicon, silver-coated plastic, nickel-coated copper, carbon-coated aluminum, silver-copper alloy, titanium-tantalum alloy, copper-chromium alloy, conductive glass, indium tin oxide (ITO) film, and polymer conductive film.

[0086] In one embodiment, the binder or the conductive material may be formed on the conductive substrate by spin coating. An advantage of spin coating is that a material in a solution state can be rapidly and efficiently distributed on a substrate with a uniform thickness. In particular, spin coating enables the formation of nanometer-scale thin films and can provide highly uniform surface quality. Furthermore, the process is simple and highly reproducible, making it potentially advantageous for application in mass production environments.

[0087] Non-limiting examples of other coating methods include dip coating, blade coating, spray coating, inkjet printing, roll-to-roll coating, thin film deposition, plasma coating, vacuum deposition, electrodeposition coating, screen printing, nanoimprint lithography, sol-gel coating, spray pyrolysis, electrochemical deposition, casting coating, spin printing, aerosol jet printing, thin film rolling, and laser ablation coating.

[0088] An advantage of the electrode for electrochemical reactions according to an embodiment of the present invention is that the electrochemical efficiency and stability of the electrode can be significantly improved through a combination of a conductive material and a binder containing liquid metal-based nanoparticles. Such an electrode provides uniform dispersion and robust adhesion characteristics, thereby minimizing structural deformation or performance degradation during charging and discharging processes. Furthermore, by maintaining excellent contact with a conductive substrate, it has the potential to operate stably even at high current densities. This can be effectively utilized in energy storage and conversion systems that require long-term reliability and performance maintenance.

[0089] Meanwhile, non-limiting examples of an electrochemical device including the above electrode include a lithium-ion battery, a lithium-polymer battery, a lithium-sulfur battery, a sodium-ion battery, a calcium-ion battery, a magnesium-ion battery, an aluminum-ion battery, an all-solid-state battery, an ultra-high capacity battery, a hybrid electrochemical capacitor, a supercapacitor, an electric double-layer capacitor, a perovskite solar cell, a silicon solar cell, an organic solar cell, a dye-sensitized solar cell, a fuel cell, a hydrogen fuel cell, a methanol fuel cell, a polymer electrolyte fuel cell, a solid oxide fuel cell, a metal-air battery, a zinc-air battery, a lithium-air battery, a flow battery, a redox flow battery, a semiconductor-based electrochemical device, a photoelectrochemical device, a photovoltaic cell, an electrochemical detector, a biosensor, an electrochemical biosensor, an environmental sensing sensor, a gas sensor, an electrolyte sensor, a pH sensor, an ion-selective sensor, an electrochemical catalyst, an electrochemical reaction cell, a CO2 reduction cell, a water electrolysis device, a seawater electrolysis device, a hydrogen generator, an ozone generator. Chlorine generator, electrochemical salt removal device, reverse electrodialysis device, electrochemical brine separation device, electrochemical device for energy storage, energy conversion device, electrochemical photocatalyst device, electrochemical material synthesis device, electrochemical ammonia synthesis device, electrochemical hydrogen storage device, electrochemical metal plating device, electrochemical desorption device, electrochemical wastewater treatment device, electrochemical recycling device, electrochemical carbon dioxide capture device, electrochemical oxygen generator, electrochemical oxidation-reduction device, electrochemical neutralization device, electrochemical hydrochloric acid generator, electrochemical organic matter decomposition device, electrochemical sterilization device, electrochemical reduction device, electrochemical water quality improvement device, electrochemical analysis device, electrochemical inspection device, electrochemical reaction analysis device, electrochemical energy storage device, electrochemical system integration device, electrochemical solid oxidation device, electrochemical regeneration device, electrochemical filtering device, electrochemical separation device, ion exchange membrane electroseparation device, electrochemical electron transfer device,Examples include electrochemical signal amplifiers, electrochemical photoelectric systems, electrochemical diagnostic devices, electrochemical biomaterial conversion devices, electrochemical biofuel cells, electrochemical metabolism measurement devices, electrochemical microfluidic devices, and electrochemical electrode fabrication devices.

[0090] The embodiments of the present invention are described below. However, the embodiments described below are merely partial embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0091] [[Example]]

[0092] As shown in FIG. 3a, in a lithium-ion battery (LIB) containing an EGaIn nanoparticle electrode stabilized by a graft copolymer, lithium ions and electrons move to the negative electrode containing EGaIn during the charging process. During the discharge process of the LIB, the alloyed lithium and EGaIn undergo an oxidation reaction to release electrons, and during the charging process of the LIB, lithium ions gain electrons, alloy with EGaIn, and undergo a reduction reaction. These reversible oxidation-reduction reactions occurring at the negative and positive electrodes can be expressed by Equation (1) and Equation (2), respectively.

[0093]

[0094] These reversible redox reactions can be advantageous as the cathode-electrolyte contact area increases due to the properties of EGaIn composed of nanoparticles. In particular, greater effects can be expected as the nanoparticles maintain their shape and size. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE-g-SPS) grafted with sulfonated polystyrene (SPS) is used not only to disperse large amounts of EGaIn into nanoparticles through mechanical shock, but also to stabilize the EGaIn nanoparticle cathode during repeated redox reactions. PVDF-TrFE-g-SPS contains a PVDF-TrFE backbone with excellent mechanical properties and strong chemical durability. Furthermore, PVDF-TrFE-g-SPS dissolves well in polar aphtosan solvents such as dimethyl sulfoxide (DMSO) thanks to its high polarity resulting from the large electric dipole moment between hydrogen and fluorine in the backbone.

[0095] Furthermore, as shown in the schematic of Fig. 3b, the high polarity dipoles of PVDF-TrFE can interact with Ga2O3 formed on the surface of finely ground EGaIn nanoparticles under a strong ultrasonic field. This allows the nanoparticles to be well dispersed and stabilized in the solvent, ultimately resulting in the formation of a self-assembled structure in which the polymer coats the surface of the EGaIn nanoparticles.

[0096] As shown in Fig. 3b, the grafted SPS was synthesized by breaking the C=C double bond in the vinyl group of 4-vinylbenzenesulfonate and attaching it between the CF bonds of the PVDF-TrFE main chain. The sulfonic acid groups of 4-vinylbenzenesulfonate have strong polarity compared to pure PVDF-TrFE, which can increase solubility in DMSO. The sulfonic acid groups located on the surface of the dispersed self-assembled EGaIn nanoparticles become negatively charged due to the release of hydrogen ions, which creates a repulsive force between the nanoparticles. This repulsive force can help inhibit the re-aggregation of EGaIn nanoparticles and, consequently, contribute to the stabilization of the EGaIn nanoparticles. Additionally, the negatively charged sulfonic acid groups on the outermost surface of the self-assembled EGaIn nanoparticles can attract positively charged lithium ions, thereby promoting the rapid movement of lithium ions. This can enable high-performance lithium-ion battery (LIB) cells even under extreme conditions such as high current density, which will be discussed in a later paper.

[0097] The 1H-NMR results in Fig. 3c indicate the successful synthesis of PVDF-TrFE-g-SPS with different graft ratios. Resonance peaks associated with PVDF-TrFE appear at 2.0–2.4 ppm and 2.6–3.2 ppm, while peaks associated with 4-vinylbenzenesulfonate are observed at 6–8 ppm. This was also confirmed by the 1H-NMR results of pure PVDF-TrFE and PVDF-TrFE-g-SPS in Fig. 3c. The graft ratio calculated based on the peak intensities in Fig. 3c was approximately 9.85%. The graft ratio can be controlled by changing the temperature, time, and composition during the synthesis process of PVDF-TrFE and poly(4-vinylbenzenesulfonate).

[0098] The dispersion of EGaIn nanoparticles with PVDF-TrFE-g-SPS in DMSO was quantitatively investigated using UV-vis absorbance spectroscopy, as shown in the schematic of Figure 3d. To investigate the dispersion of EGaIn nanoparticles according to the ratio of PVDF-TrFE-g-SPS to EGaIn, 5, 10, 15, 20, and 25 mg of PVDF-TrFE-g-SPS were added to 100 mg of EGaIn, respectively. The addition of PVDF-TrFE-g-SPS significantly increased the absorbance in the visible light wavelength range (350-800 nm). In particular, the absorbance at 500 nm increased, indicating that the dispersion of EGaIn nanoparticles was enhanced by PVDF-TrFE-g-SPS. As shown in Figure 3e, when PVDF-TrFE-g-SPS exceeded 20 mg, the dispersion enhancement stabilized, which suggests that the optimal concentration of PVDF-TrFE-g-SPS is about 20 wt%.

[0099] Subsequently, four different samples were investigated in DMSO. These were (1) a sample containing only EGaIn, (2) EGaIn dispersed in PVDF-TrFE (EGaIn@P), (3) EGaIn dispersed in a 50:50 mixture of PVDF-TrFE and PVDF-TrFE-g-SPS (EGaIn@GP(50%)), and (4) EGaIn dispersed only in PVDF-TrFE-g-SPS (EGaIn@GP(100%)). The amount of polymer binder for samples 2, 3, and 4 was kept constant at 20 mg per 100 mg of EGaIn. As shown in Figure 3f, the dispersed EGaIn particles rapidly aggregated and turned into a clear solution. The EGaIn particles dispersed in PVDF-TrFE were unstable, with most of them precipitating after 1 hour. On the other hand, the dispersion of EGaIn nanoparticles was significantly improved in samples 3 and 4 containing PVDF-TrFE-g-SPS. In particular, EGaIn@GP (100%) showed the highest opacity, which indicates that the dispersion of nanoparticles was improved due to the graft copolymer.

[0100] The dispersion state of the nanoparticles was investigated using UV-vis absorption spectroscopy on four samples, and the results are shown in Figures 3g and 3h. The addition of PVDF-TrFE-g-SPS significantly increased the absorbance in the visible light region (350-800 nm), which is consistent with the photographic results shown in Figure 3f. The stability of the dispersed EGaIn nanoparticles was evaluated by recording the absorbance at 500 nm over time. As shown in Figure 3h, the absorbance of EGaIn@GP (100%) remained almost unchanged over time, showing only a decrease of about 2.5% from the initial value, which is the result after 15 days. On the other hand, EGaIn@GP (50%) showed a more distinct decrease in absorbance at 500 nm, showing a decrease of about 15.4% after 15 days, indicating that dispersion stability decreases slightly as the PVDF-TrFE-g-SPS content decreases. EGaIn dispersed with PVDF-TrFE accelerated the instability of the nanoparticles. The low dispersion stability of EGaIn nanoparticles in PVDF-TrFE (Fig. 3h) demonstrates that grafted SPS plays an essential role in inhibiting re-aggregation. This is attributed to the negative charge characteristics of the graft chains. Zeta potential measurements (Fig. 3i) confirmed the negative charge of the SPS chains. As expected, EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) exhibited zeta potential values ​​of 28.23 mV, -76.43 mV, and -109.88 mV, respectively. A higher absolute value of the zeta potential indicates stronger interparticle repulsion, creating a more stable dispersion state. The sulfonic acid groups of the PVDF-TrFE-g-SPS coating generate repulsion between the dispersed EGaIn nanoparticles, thereby inhibiting nanoparticle re-aggregation.

[0101] The morphology and size distribution of EGaIn nanoparticles dispersed in PVDF-TrFE-g-SPS were analyzed after spin-coating on a silicon substrate. As shown in Figures 4a and 4b, the EGaIn nanoparticles had a spherical shape with an average diameter of approximately 120 nm and exhibited a relatively narrow size distribution. In contrast, EGaIn microparticles obtained after sonication without the graft copolymer (Figure 4a) had a diameter of over 200 nm and showed a larger size distribution, confirming the dispersion ability of the graft copolymer. The elemental distribution image of fluorine obtained via energy-dispersive X-ray spectroscopy (EDS) shown in Figure 4b clearly demonstrates that fluorine is uniformly distributed on the surface of the EGaIn nanoparticles. As can be seen in the transmission electron microscope (TEM) image shown in Figure 4c, a PVDF-TrFE-g-SPS film approximately 3.6 nm thick is uniformly coated on the oxide surface of the EGaIn nanoparticles. Figure 4d shows a thin EGaIn@GP film containing densely packed EGaIn nanoparticles formed on a silicon substrate.

[0102] Atomic and molecular interactions of the thin EGaIn@GP film were investigated using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), and the results are shown in Figs. 4e, 4f, and 4g, respectively. The C 1s XPS pattern in Fig. 4e shows peaks at approximately 284 eV (CC), 286 eV (CH2), and 290 eV (CF2), with no peak corresponding to C=C. However, a peak appears at approximately 287 eV (C=O), indicating that SPS was successfully synthesized on the PVDF-TrFE main chain. In the S 2p region, peaks are observed at approximately 168 eV and 170 eV, confirming that the sulfur component within the grafted polymer formed sulfonic acid groups. In the Ga 2p region, peaks appear at approximately 1118 eV (Ga3+) and 1115 eV (Ga0), indicating that gallium exists in a metallic or metal oxide form. In the 2p region, peaks appear at approximately 453 eV (In3+) and 451 eV (In0), indicating that indium also exists in a metallic or metal oxide form. The O 1s and F 1s XPS spectra confirm that the electronic structure of EGaIn nanoparticles (EGaIn@GP) stabilized with PVDF-TrFE-g-SPS is slightly altered by the graft copolymer.

[0103] Figure 4f shows the FT-IR pattern representing the interaction of PVDF-TrFE-g-SPS on the surface of EGaIn nanoparticles. The absorption peak corresponding to -CF2 in EGaIn@GP is approximately 1307 cm⁻¹. -1 It appears at, which is the peak in PVDF-TrFE-g-SPS (1309.6 cm⁻¹ -1 It is slightly lower than ). Also, the peak corresponding to -CH2 in EGaIn@GP is approximately 1406.0 cm⁻¹. -1 It appears at, which is the peak in PVDF-TrFE-g-SPS (1407.9 cm⁻¹ -1It shifts slightly compared to ). The authors interpret this shift in absorption peaks as being due to dipole-dipole interactions between the PVDF-TrFE main chain of the graft copolymer and Ga2O3 on the EGaIn surface. The vibrational frequencies of -CF2 and -CH2 are reduced due to interactions with EGaIn. The XRD results in Fig. 4g confirm that PVDF-TrFE β-phase crystals developed despite the presence of grafted side chains on PVDF-TrFE-g-SPS. In the XRD spectrum, a (110) reflection of the PVDF-TrFE β-phase crystal is observed at approximately 21°. As expected, the degree of crystallinity of PVDF-TrFE-g-SPS is lower than that of pure PVDF-TrFE. As shown in Fig. 4g (EGaIn@GP), the β-phase crystal characteristics of PVDF-TrFE-g-SPS assembled with EGaIn nanoparticles are less distinct. The authors estimate that the preferential interaction of PVDF-TrFE in EGaIn hinders the chain folding of PVDF-TrFE, resulting in a much smaller amount of β-phase crystals being formed compared to PVDF-TrFE-g-SPS.

[0104] The proposed EGaIn@GP exhibited excellent adhesion to copper substrate current collectors. Stability during lithium-ion battery (LIB) operation using copper substrates was analyzed, and the results are shown in Figures 5a and 5b. Four representative film samples were analyzed: EGaIn, PVDF-TrFE and dispersed EGaIn (EGaIn@P), 50% PVDF-TrFE-g-SPS and 50% PVDF-TrFE (EGaIn@GP(50%)), and 100% PVDF-TrFE-g-SPS (EGaIn@GP(100%)). The adhesion strength of the samples was 1.8 × 1.0 cm⁻¹. 2The weight change of samples coated on copper foil of a certain size was evaluated by measuring it before and after separating the samples from the foil using acrylic adhesive tape. As a result of examining four samples of each film, Figure 5b shows that the average weight changes of EGaIn, EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) were 12.8%, 7.3%, 4.1%, and 1.6%, respectively. These results suggest that the interfacial strength of the film on the copper foil was enhanced by incorporating PVDF-TrFE-g-SPS into EGaIn. The enhanced interface is interpreted as being caused by the increased interfacial area resulting from the low surface roughness of EGaIn@GP(100%), which consists of EGaIn nanoparticles with a narrow size distribution of 100 nm diameter. Additionally, the improved adhesion to the copper foil appears to be attributed to the thin PVDF-TrFE-g-SPS layer on the surface of EGaIn. The thin PVDF-TrFE-g-SPS film spin-coated onto copper foil exhibited superior adhesion compared to the PVDF-TrFE film.

[0105] The proposed EGaIn@GP composite possesses mechanical flexibility and self-healing capabilities, which were evaluated by verifying changes in electrical resistance during various mechanical bending tests. First, the electrical conductivity of the EGaIn@GP composite was confirmed even with the addition of PVDF-TrFE-g-SPS, demonstrating its potential for use as a lithium-ion battery (LIB) anode. The initial electrical resistance was approximately 0.9 Ω, showing almost no change even after 1,000 bending cycles at a radius of 5.2 mm. A total of 20 samples exhibited similar changes in resistance. Figure 5c illustrates the self-healing ability of EGaIn@GP, which was evaluated by monitoring changes in electrical resistance after cutting the samples and healing them with dimethyl sulfoxide (DMSO). The average change in electrical resistance across 20 EGaIn@GP samples was approximately 0.69%, indicating the potential for anodes containing EGaIn@GP to be suitable for mechanically flexible and self-healing lithium-ion batteries (Figure 5d).

[0106] PVDF-TrFE-g-SPS and EGaIn exhibited excellent wettability on copper foil surfaces in combination with PVDF-TrFE-g-SPS. The results for EGaIn@GP in both liquid and solid states demonstrate that dipole interactions between PVDF-TrFE and EGaIn nanoparticles promote the dispersion of EGaIn nanoparticles in dimethyl sulfoxide (DMSO) upon sonication. Simultaneously, the dispersed nanoparticles effectively inhibited re-aggregation with one another while grafted with SPS chains containing sulfonic acid groups. Furthermore, negatively charged SPS chains act to induce positively charged lithium ions to the surface of EGaIn nanoparticles during charging through self-assembly on the nanoparticle surface, which can lead to high-performance lithium-ion batteries with excellent stability.

[0107] Based on the molecular and structural characteristics of EGaIn@GP, the authors propose that EGaIn@GP is suitable for lithium-ion batteries as a high-conductivity and high-capacity anode due to its conductive network and structural stability (Fig. 6a). The electrochemical characteristics of EGaIn@GP were evaluated in a CR2023 coin-type half-cell in a voltage range of 0.01–3.0 V. The differential capacity (dQ / dV) curves of the half-cell lithium-ion battery containing the EGaIn@GP anode shown in Fig. 6b exhibit peaks at 0.70, 0.54, and 0.47 V, which are related to the alloying reaction of gallium and indium with lithium during the charging process. During the discharge process, peaks are exhibited at 0.90, 0.78, and 0.49 V, which are related to the dealloying reaction of gallium and indium.

[0108] Even after repeated charge-discharge cycles, the area under the dQ / dV curve remains constant and the peak position appears the same, demonstrating that the charge-discharge process is reversible. A comparison of the dQ / dV curve shapes of half-cells containing EGaIn@P, EGaIn@GP (50%), and EGaIn@GP (100%) cathodes showed that the peak position did not change even when using different cathode materials. As shown in Fig. 6c, the half-cell lithium-ion battery containing the EGaIn@GP cathode exhibited capacities of 771.9, 711.9, 599.0, 465.0, and 320.5 mAh / g at 0.1, 0.2, 0.5, 1.0, and 2.0 A / g, respectively. In each graph, the plateau at approximately 0.75 V indicates a two-phase reaction during the alloying / dealloying between lithium and EGaIn.

[0109] The electrochemical characteristics of EGaIn@GP (100%) were compared with those of EGaIn@P and EGaIn@GP (50%) through half-cell lithium-ion battery (LIB) tests. To investigate the effect of the graft copolymer on rate performance, evaluations were performed on all three half-cells at current densities of 0.1, 0.2, 0.5, 1.0, and 2.0 A / g. As shown in Figure 6d, the three half-cells exhibited specific capacities of 782.5, 731.2, and 694.0 mAh / g, respectively, at 0.1 A / g. As the graft copolymer ratio decreased, the capacity of the half-cells clearly decreased as the current density increased. The rate performance, comparing capacity at high current density (2.0 C) and low current density (0.1 C), was 45.1%, 32.3%, and 13.8% for the EGaIn@P, EGaIn@GP (50%), and EGaIn@GP (100%) anodes, respectively. Additionally, after cycling at a high current density of 2.0 A / g, the half-cell LIBs exhibited capacities of 774.3, 698.8, and 640.0 mAh / g when switched to a low current density of 0.1 A / g, respectively, and the recovery rates were calculated to be 99.0%, 95.6%, and 92.4%, respectively. These results suggest that sulfonic acid groups grafted onto PVDF-TrFE-g-SPS effectively stabilize the EGaIn nanoparticle complex, thereby improving battery performance at high current densities where efficient charge transfer is critical.

[0110] The long-term cycling performance of the LIB half-cell containing the EGaIn@GP cathode was evaluated at 0.5 A / g, and the results are shown in Fig. 7a. The LIB half-cell exhibited an initial capacity of 670.6 mAh / g and a Coulomb efficiency of 98.0%. After 500 cycles, the cathode maintained a capacity of 566.5 mAh / g and a high Coulomb efficiency of 99.9%. Comparative experiments were performed at a high current density of 1.0 A / g on LIB half-cells containing EGaIn@GP (100%), EGaIn@GP (50%), and EGaIn@P cathodes. Fig. 7b clearly demonstrates the improved cycling stability of EGaIn@GP (100%). The initial capacities of EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) were 522.7, 396.0, and 225.0 mAh / g, respectively, and decreased to 365.0, 183.2, and 17.7 mAh / g, respectively, after 100 cycles. The EGaIn@GP(100%) and EGaIn@GP(50%) anodes maintained 69.8% and 46.2% of their initial capacities, respectively, while the EGaIn@P anode lost its substantial charge-discharge characteristics after about 40 cycles. Increasing the graft copolymer ratio suppressed the decrease in capacity, which is interpreted as a result of the graft copolymer containing sulfonic acid groups stabilizing the EGaIn nanoparticles.

[0111] To further investigate the cycling stability of the EGaIn@P, EGaIn@GP(50%), and EGaIn@GP(100%) cathodes, impedance spectroscopy (EIS) was performed after 20 charge-discharge cycles at 0.5 A / g, and the results are shown in Fig. 7c. The Nyquist plot shows a semicircle at high frequencies and a straight line at low frequencies, representing the internal resistance (Re), charge transfer resistance (Rct), and Warburg resistance of the battery. The lithium ion diffusion coefficient (DLi) is (Z': impedance on the horizontal axis, w: angular frequency) and diffusion equation It was estimated using . Here, n represents the number of electrons per molecule during the redox reaction, and σ represents the Warburg coefficient. σ is It is calculated from the slope of, and the equation It can be obtained through [this]. Since other constant and parameter values ​​are already known, the lithium ion conductivity of the three LIB half-cells could be qualitatively compared using the values ​​in Fig. 7c and Fig. 7d.

[0112] As shown in Fig. 7c, the charge transfer resistance (Rct) of LIB half-cells containing EGaIn (100%), EGaIn (50%), and EGaIn@P cathodes was 205.5, 402.7, and 572.7 Ω, respectively. Fig. 7d shows that the impedance near the y-intercept and the slope of the graph decrease with increasing graft polymer ratio in the high frequency region, indicating an increase in the lithium ion diffusion coefficient. This suggests that the graft polymer forms ion channels through sulfonic acid groups, thereby stabilizing the composite EGaIn nanoparticles and promoting lithium ion diffusion.

[0113] Increasing the proportion of grafted polymer increases the concentration of sulfonic acid groups, which stabilizes EGaIn nanoparticles and promotes ion conduction, thereby improving the lithium ion diffusion rate. These observations demonstrate that the electrochemical performance of the system has improved. However, it should be noted that while negatively charged sulfonic acid groups can effectively attract lithium ions during charging, they may hinder the movement of lithium ions during discharging.

[0114] Figures 7e and 7f confirm that the EGaIn nanoparticles remained intact even after long-term cycling tests of a LIB half-cell containing an EGaIn@GP cathode. Even after more than 200 cycles at 0.5 C, the EGaIn nanoparticles remained well dispersed within the film, similar to their initial state. In contrast, the half-cell with an EGaIn cathode without PVDF-TrFE-g-SPS developed significant mechanical cracks after the cycling tests.

[0115] The results observed in this invention demonstrate that the proposed strategy for dispersing and stabilizing EGaIn nanoparticles using PVDF-TrFE-g-SPS effectively mitigates volume changes during lithium insertion and minimizes mechanical cracking of the anode during lithium ion removal. This suggests the possibility of developing novel LIB half-cells featuring self-healing and deformable EGaIn anodes.

[0116] [[conclusion]]

[0117] The present invention demonstrated that an ionomer-grafted fluorinated polymer is suitable for the dispersion and stabilization of liquid metal EGaIn nanoparticles and can promote ion transfer to the surface of EGaIn. This enables the development of a new mechanically deformable and self-healing cathode for use in lithium-ion batteries (LIBs). EGaIn nanoparticles with a diameter of approximately 200 nm were effectively dispersed and stabilized by the graft copolymer PVDF-TrFE-g-SPS. The PVDF-TrFE main chain was preferentially adsorbed onto the surface of the EGaIn nanoparticles, and the grafted ionomer SPS sufficiently separated the EGaIn nanoparticles to suppress re-aggregation of the nanoparticles.

[0118] In addition, ion channels formed by self-assembled SPS chains on the surface of EGaIn nanoparticles facilitated the migration of lithium ions from the electrolyte to the EGaIn surface, enabling effective electrochemical reduction of lithium ions on the surface of EGaIn nanoparticles. A half-cell LIB comprising a flexible, self-healing, and highly adhesive cathode composed of EGaIn nanoparticles stabilized by a graft copolymer exhibited excellent stability (85% retention rate after 500 charge-discharge cycles, 0.5 A / g), rate performance (45.1% at 2.0 A / g), and battery capacity (803.7 mAh / g at 0.1 A / g).

[0119] The solution process-based approach proposed in this invention, utilizing the self-assembly of EGaIn and graft copolymers, is scalable and provides a simple and robust method for designing flexible, self-healing electrodes suitable for large-scale and high-speed processing. This approach opens up possibilities for use in various energy storage applications.

[0120] [[Experimental Method]]

[0121] Materials: Polyvinylidene fluoride (PVDF-TrFE, molecular weight 4,000,000 g / mol) used in the synthesis of a graft copolymer binder containing 25% molar fraction trifluoroethylene (TrFE) was purchased from Solvay, Belgium. Sodium 4-vinylbenzenesulfonate, monovalent copper chloride (CuCl), and 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) were purchased from Sigma-Aldrich Korea. All organic solvents, including methanol, dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and a eutectic alloy (EGaIn) of 75.5% gallium and 24.5% indium, were purchased from Sigma-Aldrich Korea. Ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (EC / DMC / EMC, 1:1:1, volume ratio) and 5 volume% of fluoroethylene carbonate used as lithium-ion battery (LIB) electrolytes were purchased from Starlyte.

[0122] Measurement equipment: The synthesis of the graft copolymer binder was confirmed using FT-NMR (400 MHz Fourier Transform NMR Spectrometer, Bruker BioSpin AVANCE III HD 400). The morphology of the EGaIn / graft copolymer composite was analyzed using FE-SEM (Field Emission Scanning Electron Microscopy, JEOL 7610-plus). The composite was further analyzed using HR-XRD (High Resolution X-ray Diffraction, Rigaku SmartLab), FT-IR (Fourier Transform Infrared Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), and UV-vis spectroscopy (JASCO V-650). The electrochemical characteristics of the LIB half-cell, such as dQ / dV versus potential, charge / discharge characteristics, capacity, and EIS (Electrochemical Impedance Spectroscopy), were measured using a potentiostat / galvanostat (VMP3, Princeton Applied Research).

[0123] Synthesis of Graft Copolymer: PVDF-TrFE (1 g, molecular weight 4,000,000 g / mol) was dissolved in DMSO (10 mL), and sodium 4-vinylbenzenesulfonate (6 g) was dissolved in NMP (15 mL). The two solutions were purged with argon and then mixed. HMTETA (0.05 mL) and CuCl (0.01 g) were added to the mixture as catalysts, and the mixture was stirred in an oil bath at 120°C for 5 days. The synthesized material was washed with a solution of deionized water and methanol mixed in a 2:1 volume ratio, and then dried at 70°C for 12 hours. This washing and drying process was repeated to finally obtain the graft copolymer.

[0124] Preparation of EGaIn and Graft Copolymer Dispersion Solution: To prepare an EGaIn@GP composite solution by mixing and dispersing EGaIn and PVDF-TrFE-g-SPS, a graft copolymer (0.02 g) was dissolved in DMSO (10 mL), and EGaIn (0.1 g) was added. The solution was treated with ultrasonic dispersion (40% amplitude, 5 seconds operation, 5 seconds pause) for 40 minutes. Afterward, the dispersed solution was centrifuged at 15,000 rpm for 10 minutes to remove the unreacted polymer at the top. To prepare an EGaIn@P composite solution, PVDF-TrFE (0.02 g) was added instead of the graft copolymer. For the EGaIn@GP (50%) composite solution, a graft copolymer (0.01 g) and PVDF-TrFE (0.01 g) were added.

[0125] Fabrication of a LIB half-cell containing an EGaIn / PVDF-TrFE-g-SPS cathode: Carbon black (0.01 g) was added to an EGaIn / PVDF-TrFE-g-SPS dispersion solution, and the mixture was further treated for 10 minutes using ultrasonic dispersion (40% amplitude, 5 seconds operation, 5 seconds pause). The dispersion solution was drop-cast onto copper foil and dried at 40°C for 12 hours to obtain 1 mg / cm² 2 A cathode containing a coating of electrode material was prepared. A half-cell consisting of a cathode, a lithium coin electrode, a Celgard 2400 separator, and 1M LiPF6 electrolyte in EC / EMC / DEC was assembled in an argon glove box and dried in a 25°C oven for 1 day.

[0126] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims. Explanation of the symbols

[0127] 100: Liquid metal-based nanoparticles 110: Liquid metal-containing droplet nanoparticles 120: Ionomer-grafted copolymer 200: Electrochemical reaction electrode S210: Dispersion step in the manufacturing process of electrochemical reaction electrodes

Claims

Claim 1 Liquid metal-based nanoparticles comprising: droplet nanoparticles containing liquid metal; and an ionomer-grafted copolymer coated on the surface of the droplet nanoparticles. Claim 2 In claim 1, the liquid metal comprises a eutectic alloy of gallium and indium (EGaIn), and is a liquid metal-based nanoparticle. Claim 3 In claim 1, the ionomer is a liquid metal-based nanoparticle comprising sulfonated polystyrene (SPS) functionalized with sulfonic acid groups. Claim 4 In claim 1, the copolymer is a liquid metal-based nanoparticle, which is a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE). Claim 5 In claim 4, the ionomer grafted onto the copolymer comprises sulfonated polystyrene (SPS) functionalized with sulfonic acid groups, and the ratio of the ionomer grafted onto the copolymer is 9 to 10%, the liquid metal-based nanoparticle. Claim 6 In claim 4, the liquid metal-based nanoparticles, wherein the trifluoroethylene (TrFE) in the copolymer is 20 to 30 mol%. Claim 7 A method for manufacturing liquid metal-based nanoparticles, comprising: a dispersion step of dispersing a liquid metal in a solution containing a copolymer grafted with an ionomer; wherein, in the dispersion step, the copolymer is coated on the surface of a droplet nanoparticle containing the liquid metal. Claim 8 A method for manufacturing liquid metal-based nanoparticles according to claim 7, wherein the liquid metal comprises a eutectic alloy of gallium and indium (EGaIn). Claim 9 A method for manufacturing liquid metal-based nanoparticles according to claim 7, wherein the ionomer comprises sulfonated polystyrene (SPS) functionalized with sulfonic acid groups. Claim 10 A method for producing liquid metal-based nanoparticles according to claim 7, wherein the copolymer is a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE). Claim 11 A method for producing liquid metal-based nanoparticles according to claim 10, wherein the ionomer grafted onto the copolymer comprises sulfonated polystyrene (SPS) functionalized with sulfonic acid groups, and the ratio of the ionomer grafted onto the copolymer is 9 to 10%. Claim 12 A method for manufacturing liquid metal-based nanoparticles according to claim 10, wherein the trifluoroethylene (TrFE) in the copolymer is 20 to 30 mol%. Claim 13 A binder for an electrochemical reaction electrode comprising liquid metal-based nanoparticles, comprising: droplet nanoparticles containing liquid metal; and an ionomer-grafted copolymer coated on the surface of said droplet nanoparticles. Claim 14 A binder for an electrochemical reaction electrode according to claim 13, wherein the liquid metal comprises a eutectic alloy of gallium and indium (EGaIn), the ionomer comprises sulfonated polystyrene (SPS) functionalized with sulfonic acid groups, the copolymer comprises a copolymer of polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE), and the ratio of the ionomer grafted onto the copolymer is 9 to 10%. Claim 15 An electrode for an electrochemical reaction comprising: a binder for an electrochemical reaction electrode according to claim 13; a conductive material mixed with said binder; and a conductive substrate having said binder and said conductive material formed on its surface.

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