Method for manufacturing metal nanocatalyst for secondary battery with improved active metal dispersibility and metal nanocatalyst for secondary battery manufactured using same

Abstract

The invention relates to a method for manufacturing a metal-supported catalyst for use in a battery. The present invention presents, as one embodiment, a method for manufacturing a metal-supported catalyst, the method comprising: a first step of adding an alcohol compound to a metal salt or a metal acid to prepare a metal precursor; a second step of preparing a carrier and adding the metal precursor prepared in the first step to the carrier; a third step of adjusting the pH of the carrier into which the metal precursor obtained through the second step has been added; a fourth step of heating a mixture of the metal precursor obtained through the third step and the carrier to reduce metal particles to thereby generate a catalyst; a fifth step of mixing and aging the catalyst generated through the fourth step; a sixth step of filtering, washing, and drying the catalyst aged through the fifth step to remove impurities; and a seventh step of pulverizing the catalyst generated through the sixth step.

Description

Method for preparing a metal nanocatalyst for secondary batteries with improved active metal dispersibility and a metal nanocatalyst for secondary batteries prepared using the same

[0001] The present invention relates to a method for manufacturing a metal catalyst, and more specifically, to a method for manufacturing a metal catalyst for a battery anode (negative electrode) in which metal nanoparticles are supported on a carrier.

[0002] A lithium-ion battery is an electrochemical device composed of a cathode, an anode, and an electrolyte, and these three elements play a role in storing and releasing energy through the movement of lithium ions.

[0003] In lithium-ion batteries, energy is stored and released by repeatedly performing charging, in which lithium ions move from the positive electrode to the negative electrode to store energy, and discharging, in which lithium ions move from the negative electrode to the positive electrode to generate current and release energy during this process.

[0004] In this case, carbon is primarily used as the anode (negative electrode) of lithium-ion batteries. As the main material for the battery negative electrode, carbon provides a structure capable of absorbing and storing lithium ions. Furthermore, this carbon material reacts well with lithium ions in a solid state and offers high electrical conductivity and stability.

[0005] However, when using only carbon in the anode as described above, it was difficult to suppress lithium dendrite formation (tree-branch-shaped crystals formed when using lithium-ion batteries). Therefore, a catalyst for an anode with excellent durability is required to solve this problem.

[0006] The present invention provides a method for manufacturing a metal catalyst for an anode that can be used in the anode (negative electrode) of a battery to suppress lithium dendrite formation and improve battery performance.

[0007] In addition, we present a method for manufacturing a metal catalyst that utilizes an alcohol compound to improve the dispersibility of metal particles and can produce a metal catalyst for an anode with improved initial battery performance and durability.

[0008] Other detailed objectives of the present invention will be clearly understood and grasped by experts or researchers in this technical field through the specific details described below.

[0009] To solve the above problem, the present invention provides, as an embodiment, a method for manufacturing a metal-supported catalyst used in a battery, comprising: a first step of preparing a metal precursor by adding an alcohol compound to a metal salt or a metal acid; a second step of preparing a carrier and introducing the metal precursor prepared in the first step into the carrier; a third step of adjusting the pH of the carrier into which the metal precursor obtained through the second step has been introduced; a fourth step of generating a catalyst by reducing metal particles through heating a mixture of the metal precursor obtained through the third step and the carrier; a fifth step of mixing and aging the catalyst generated through the fourth step; a sixth step of removing impurities by filtering, washing, and drying the catalyst aged through the fifth step; and a seventh step of grinding the catalyst generated through the sixth step.

[0010] Here, the metal precursor manufactured in the first step above may be a silver precursor.

[0011] Meanwhile, the carrier used in the second step above may be a carbon carrier.

[0012] In addition, the alcohol compound used in the first step above may be at least one of ethylene glycol, propylene glycol, and glycerol.

[0013] According to an embodiment of the present invention, a catalyst capable of improving secondary battery performance can be prepared by reducing metal ions through a solvent material having a hydroxyl group (-OH) and improving dispersibility.

[0014] Specifically, performance can be improved by introducing an active metal with enhanced dispersibility into the anode used in secondary batteries. In addition, uniform metal nanoparticle-based catalysts can improve the durability of secondary batteries.

[0015] Other effects of the present invention will be clearly grasped and understood by experts or researchers in the art through the specific details described below or during the process of implementing the present invention.

[0016] FIG. 1 is a flowchart illustrating a method for manufacturing a metal nano catalyst for a secondary battery according to an embodiment of the present invention.

[0017] FIG. 2 is an XRD peak diagram showing the lattice type of Ag / C catalyst particles prepared according to the embodiment and comparative example of the present invention.

[0018] FIG. 3 is a diagram showing the size of Ag / C catalyst particles prepared according to an embodiment and a comparative example of the present invention.

[0019] Figure 4 is an EDS photograph showing the catalyst particle size of Ag / C prepared according to an embodiment of the present invention.

[0020] Figure 5 is a TEM image showing the size of Ag / C catalyst particles prepared according to an embodiment of the present invention.

[0021] FIG. 6 is a graph showing the distribution of Ag / C catalyst particles prepared according to an embodiment of the present invention.

[0022] FIG. 7 is an SEM image showing an Ag / C catalyst prepared according to an embodiment of the present invention.

[0023] FIG. 8 is a graph showing the results of evaluating the catalyst charge and discharge efficiency of Ag / C prepared according to the embodiments and comparative examples of the present invention.

[0024] FIG. 9 is a graph showing the durability evaluation results of an Ag / C catalyst prepared according to an embodiment of the present invention.

[0025] The features and effects of the present invention described above will become clearer through the following detailed description in conjunction with the attached drawings, and accordingly, a person skilled in the art to which the present invention pertains will be able to easily implement the technical concept of the present invention. 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 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. The terms used in this application are used merely to describe specific embodiments and are not intended to limit the present invention.

[0026] Hereinafter, a method for manufacturing a metal catalyst according to one embodiment of the present invention will be described in detail with reference to the drawings.

[0027] A method for manufacturing a metal catalyst according to an embodiment of the present invention comprises the steps of: i) manufacturing a metal precursor; ii) mixing the metal precursor with a support; iii) adjusting the pH of the mixed metal precursor and support; iv) reducing an active metal to form a catalyst; v) aging the formed catalyst; vi) filtering and drying the aged catalyst; and vi) grinding the dried catalyst.

[0028] Each step below is described in detail with reference to the drawings.

[0029] FIG. 1 is a flowchart illustrating a method for manufacturing a metal catalyst for a battery anode according to an embodiment of the present invention.

[0030] As a first step, a metal precursor is manufactured (101)

[0031] The metal precursor serves to provide metal particles supported on the carrier. The metal particles for the battery anode are not specific, and materials such as Ag (silver), In (indium), Sn (tin), and Cu (copper) can be used.

[0032] In this manner, the metal precursor supplying the metal particles is not limited to a specific metal, but the present invention describes the use of Ag metal capable of alloying and reversibly reacting with Li (lithium).

[0033] Various ligand materials can be used as metal salts for utilizing Ag metal. Metal salt precursors are not limited to metal salts or metal acids, such as silver acetate (Ag Acetate), silver oxalate (Ag Oxalic Acid), silver chloride (Ag Chloride), and silver nitrate (Ag Nitrate).

[0034] In the following examples, silver nitrate was used as an example. Silver nitrate can be dissolved in various solvents, and a complex ionizing agent may be added as needed for complex ionization. Specifically, the complex ionizing agent is a substance such as ammonia (NH3) and carbon monoxide (CO), but is not limited to specific substances.

[0035] Meanwhile, the solvent used for the manufacture of the metal precursor may include a solvent that generates a proton (H+) when oxidation occurs. Related substances may include any substance having an -OH functional group, such as primary alcohols, secondary alcohols, and tertiary alcohols, such as ethylene glycol, propylene glycol, and glycerol.

[0036] In the following, ethylene glycol was used as an example. Substances having -OH functional groups are oxidized near their boiling point to exist as aldehydes, and protons (Proton, H +It generates protons. The generated protons reduce the active metal, thereby proceeding with the metallization of the metal precursor. This process can reduce the ionized metal on the support to form a metallic phase and improve the degree of metal dispersion.

[0037] Meanwhile, a capping agent can be used to control the particles and improve the dispersion of the active metal. As is already widely known, capping agents such as PVP (Polyvinylpyrrolidone), PVA (polyvinyl alcohol), and organic acids (oleic acid) can be added in a weight ratio relative to the active metal. These materials form organic ligands on the active metal, which can suppress particle aggregation at high temperatures. Furthermore, the highly dispersed active metal induces smooth lithium adsorption and desorption in secondary battery reactions.

[0038]

[0039] In the second step, the precursor and the carrier are mixed (102)

[0040] To this end, a carrier is prepared. The carrier material used is not limited, and any material capable of bonding with Li, such as magnesium oxide (MgO), silicon, and carbon, can be used. In this case, carbon is suitable as it is used in existing anodes and can bond with Li. Carbon is a widely used material in anodes and can store Li, allowing it to properly perform charging and discharging functions.

[0041] The carbon used is not limited to types such as Ketjen black. In particular, the carbon used for the anode is preferably plate-shaped, more preferably spherical, and most preferably surface-treated carbon.

[0042] In the case of spherical carbon, the specific surface area and particle size may be reduced to achieve carbon density. The particle size of carbon is approximately 40–80 nm; for particles larger than this, Li mobility may be degraded due to the expansion of the storage material. This reduces the charge and discharge performance of the battery. On the other hand, particles smaller than 40 nm find it difficult to store sufficient Li.

[0043] A metal precursor is introduced into and mixed with the carrier. The reactor used to mix the prepared metal precursor and the carrier is not limited to a specific reactor, and various reactors such as ribbon mixers and planetary mixers can be utilized.

[0044] Meanwhile, carbon can be dispersed in an ethylene glycol solvent for mixing with a metal precursor and a carrier. At this time, carbon can be dispersed in the solvent regardless of the method used, such as high-pressure dispersion or the method using a homomixer, which are widely known dispersion methods to date.

[0045] The manufactured metal precursor can be added to the carrier in the form of droplets to ensure uniform dispersion. A pump can be used for this droplet dispersion, and it is preferable to use a metering pump to add the precursor to the carrier.

[0046] Although the dropwise addition rate of the solution is not limited, it must be carried out at the slowest possible speed to ensure uniform dispersion on the support. To this end, a calibrated peristaltic pump can be used to dropwise add the metal precursor. Through this process, a metal catalyst can be produced.

[0047]

[0048] As a third step, the pH of the mixed metal precursor and carrier is adjusted (103).

[0049] pH adjustment can be performed to achieve high dispersion of the active metal Ag. Various widely known substances such as NaOH, NaCO3, KOH, and KCO3 can be used for pH adjustment.

[0050] The concentration of the basic substance used as a pH adjuster is preferably 1 to 3 M. If the concentration is less than 1 M, a large amount of solvent must be used for pH adjustment. It is difficult to control the pH of the metal precursor and carrier mixture with pH adjusters of 3 M or higher.

[0051] At this time, the controlled pH is preferably 10 to 12. If the pH is less than 10, it is difficult to expect high dispersion of the active metal, and particle aggregation occurs. If the pH is higher than 12, it is difficult to expect improvement in secondary battery performance due to unreduced active metal.

[0052] These pH adjusters can be added at 25°C, but there is no temperature restriction. As is already widely known, mixing methods can be performed using various methods such as magnetic bars, planetary mixers, and ribbon mixers.

[0053]

[0054] In the fourth step, an active metal is reduced to form a catalyst (104)

[0055] The reduction of the active metal is performed at the boiling point of the solvent. As previously described, alcohol compounds such as ethylene glycol can reduce the active metal by generating protons near their boiling point. The reduction temperature is preferably 100–180°C. It is difficult to expect proper reduction of the active metal at temperatures lower than 100°C. If reduction is performed at temperatures higher than 180°C, it causes aggregation of the active metal, making it difficult to expect improvement in secondary battery performance.

[0056] At this time, the reduced metal particles need to be controlled to an appropriate size. It is preferable that the metal nanoparticles used in the present invention be 200 nm or smaller. In particular, when silver nanoparticles are used, the particle size is 100 nm or smaller, and preferably, a size of 10 to 100 nm is appropriate.

[0057] If the size of Ag nanoparticles is larger than 100 nm, the size of Ag bound to Li increases, causing anode expansion and potentially impairing battery performance. If it is smaller than 10 nm, the increase in amorphous Ag makes it difficult to expect improvements in battery charge and discharge performance or dendrite suppression.

[0058] In addition, the surface state of the metal nanoparticles used must be free of oxygen. During the charging and discharging process, Li ions can combine with oxygen to form Li2O. Such irreversible reactions can accelerate the dendrite formation of Li.

[0059]

[0060] In the fifth step, the generated catalyst is mixed and aged (105)

[0061] The catalyst, having completed the dropwise addition of the precursor according to the above-described process, is subjected to continuous mixing and aging to ensure that metal particles are uniformly distributed on the surface of the support. Aging is not limited to a specific time, but the longer the aging process, the higher the degree of metal dispersion.

[0062] However, since an excessively long time can increase the catalyst manufacturing process time and result in an inefficient catalyst manufacturing system, mixing and maturation must be carried out according to an appropriate time.

[0063] The shape of the impeller used for mixing is not limited to ribbon, 3-way, 4-way, sawtooth type, etc. The stirring speed of the impeller should be performed at a speed at which the powder vortex is properly formed.

[0064] The temperature suitable for catalyst preparation is room temperature (20–30°C), and if it is higher, metal nanoparticles may aggregate. When mixing and aging at a temperature lower than the suitable temperature, it is difficult to expect uniform dispersion of the metal precursor. Therefore, a jacketed reactor was used to maintain a constant temperature.

[0065]

[0066] In the sixth step, the aged catalyst is filtered and dried (106)

[0067] The catalyst, once mixed, can be separated from the reaction solution by filtration and washing processes to remove residual compounds or impurities used in the reaction. Subsequently, impurities in the catalyst can be further removed through a drying process. The drying method is not specified, such as a vacuum oven or a convection oven, but preferably, a vacuum oven can be used. Additionally, when using a convection oven, drying can be performed in a nitrogen (N2) atmosphere.

[0068] The appropriate drying temperature is 60 to 80°C, and at temperatures lower than this, volatile substances or moisture cannot evaporate, which may degrade battery performance. If dried at temperatures above the appropriate temperature, the viscosity of the anode slurry increases due to the clumping of metal particles, which may make battery manufacturing difficult.

[0069] The drying time is not specified, but can be performed for 6 to 24 hours. If the drying time is less than 6 hours, it is difficult for catalyst impurities to volatilize. If drying is 24 hours or longer, the time required for the catalyst manufacturing process increases, and aggregation of metal nanoparticles may occur.

[0070]

[0071] In the seventh step, the dried catalyst is crushed (107)

[0072] The manufactured catalyst can be pulverized through grinding. The grinding method used in the grinding process is not limited. For example, the pulverization of the dried catalyst can be performed using a high-speed mixer.

[0073] Grinding is a process of adjusting the metal catalyst formed after reduction to an appropriate particle size. By controlling the particle size of the catalyst through the grinding process, the reaction surface area increases and catalyst efficiency is improved. The more uniform the particle size of the catalyst, the more consistent performance can be guaranteed in the reaction. To make the catalyst particles uniform, the grinding process can be performed 1 to 2 times for 1 to 2 minutes to obtain the final metal catalyst.

[0074]

[0075] A metal catalyst can be manufactured through such a manufacturing process. Figure 7 illustrates an Ag / C catalyst as an example of such a metal-supported catalyst. The manufactured Ag / C catalyst has high Ag dispersibility and particle uniformity, which not only improves the charging and discharging efficiency of a secondary battery but also improves the durability of the secondary battery due to the dispersed Ag.

[0076]

[0077] Next, an example of a method for manufacturing a metal-supported catalyst according to one embodiment of the present invention will be described in detail. The following example is merely illustrative of one form of the present invention, and the scope of the present invention is not limited by the following example.

[0078] Examples

[0079] An Ag precursor was prepared by adding ethylene glycol to 1M silver nitrate (Ag nitrate). Meanwhile, a carbon support was added to 1,000 mL of ethylene glycol and mixed using a homo mixer at 13,500 rpm for 30 minutes. The Ag precursor was then mixed with the dispersed support using a peristaltic pump. At this stage, the Ag precursor was added to ensure that 15 wt% of Ag was supported. A 1M KOH solution was prepared by dissolving KOH flakes in purified water and was added dropwise to the mixture of the Ag precursor and support to achieve a pH of 10–12. The prepared mixture was heated at a rate of 5°C / min until it reached 100°C. After reaching 100°C, the solution was aged for 2 hours to allow the active metal to be sufficiently reduced. The Ag / C catalyst obtained after reduction was filtered and then thoroughly washed with water, ethanol, or acetone to ensure no residual ethylene glycol remained. The washed catalyst was placed in a vacuum oven to dry, and then dried again at room temperature for 24 hours. The dried catalyst was ground using a mixer to finally produce a catalyst with 15 wt% Ag / C.

[0080]

[0081] Comparative example

[0082] A metal precursor was prepared by adding 1M silver nitrate (Ag nitrate) and 1M MEA (amine compound). Meanwhile, carbon (Super P, Emeris) was prepared as a support and introduced into a double-jacketed reactor. To mix and mature the metal precursor, the Ag precursor was added to the carbon using a peristaltic pump. At this time, the temperature of the double-jacketed reactor was set to 25 ℃, and the Ag precursor was introduced to ensure 15 wt% Ag was supported. To ensure uniform Ag support, the catalyst was matured for 12 hours to produce an Ag / C catalyst. Subsequently, the catalyst was dried in a vacuum oven at 80 ℃ for 12 hours. The Ag / C catalyst was micronized through a grinding process, and finally, a 15 wt% Ag / C catalyst was prepared.

[0083]

[0084] Evaluation example

[0085] For the Ag / C catalysts prepared according to the examples and comparative examples, the particle shape, particle size, and dispersion of Ag were measured, and the characteristics when used as electrodes for secondary batteries were measured and evaluated.

[0086] Ag particle size and crystal structure (XRD)

[0087] The crystallinity and particle size of the Ag / C catalyst were analyzed using an X-ray diffractometer (XRD, SmartLab High Temp, Rigaku, Tokyo, Japan) and copper Kα radiation (Cu Ka radiation, 0.154 nm). Measurements were performed at intervals of 5° / min within a 2θ range of 5–90°. Additionally, the general-purpose pattern analysis program SmartLab Program was utilized to verify the crystal structure patterns of the samples. Particle size was calculated using the Scherrer equation as shown below.

[0088]

[0089] The crystallinity of Ag supported on a carbon carrier was referenced from JCPDS NO. 04-0783. The results of the above analysis are shown in Figures 2 and 3.

[0090] Referring to the drawings, the catalyst prepared according to the example was measured to have a smaller particle size compared to the catalyst prepared according to the comparative example, and an Ag metallic phase was observed. Furthermore, similar particle sizes were measured on all lattice planes, confirming that Ag of uniform size was supported on the carbon.

[0091]

[0092] Ag particle shape, size, and dispersion (TEM, EDS)

[0093] Transmission Electron Microscope (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) (JEM-ARM200F, NEOARM) analysis was performed to determine the particle shape and size of Ag supported on the carbon support of the Ag / C catalyst prepared according to the example. The results are shown in Figures 4 and 5.

[0094] The particle size of Ag supported on carbon was measured through TEM analysis. It was confirmed that Ag was uniformly supported at magnifications of 50 nm and 100 nm, which was similar to the XRD data.

[0095] Meanwhile, to confirm the distribution of Ag particles, an Ag / C catalyst was mixed with 50 ml of ethanol in a vial, placed on a copper grid, and ultrasonically dispersed for 1 minute. In addition, to confirm the distribution of Ag nanoparticles, the size of 100 particles was measured, and the particle distribution results are shown in Figure 6.

[0096] When the dispersion of Ag nanoparticles was measured through EDS analysis, it was confirmed that Ag of uniform size was loaded onto carbon. Based on 100 Ag nanoparticles, the average particle size was approximately 12 nm, and it was confirmed that the particle distribution was uniform.

[0097]

[0098] Secondary battery electrode evaluation (anode)

[0099] For the evaluation of the anode electrode, 4g of the Ag / C catalyst prepared in the example and comparative example and 4g of an NMP solution containing 7wt% of PVdF (polyvinylidene fluoride) were placed in a Thinky mixer container and mixed three times for 6 minutes each at 1,500 rpm to form a slurry.

[0100] To confirm the dispersion of Ag, SEM analysis was performed on the Ag / C catalyst according to the example before and after slurrying, and the results are shown in Fig. 7. As shown, it was confirmed that the dispersion of Ag within the carbon was uniform in both the catalyst before and after slurrying.

[0101] Subsequently, a monocell was manufactured by supporting an Ag / C catalyst slurry on a SUS foil. The charge and discharge cycle characteristics of the monocell were evaluated under operating voltage ranges of 4.25V-3.0V and operating temperature of 60℃, and the results are shown in Figures 8 and 9.

[0102] Referring to the drawings, when compared to the comparative example, the 15Ag / C anode prepared in the example showed high activity in terms of initial charge and discharge efficiency. As a result of the durability test, the catalyst according to the comparative example experienced an electrode short circuit after 30 cycles, whereas the catalyst according to the example showed stable activity even after 30 cycles.

[0103] Although the detailed description of the present invention described above has been explained with reference to preferred embodiments of the invention, those skilled in the art or those with ordinary knowledge in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and technical scope of the invention as described in the claims set forth below.

Claims

1. A method for manufacturing a metal-supported catalyst used in a battery, A first step of preparing a metal precursor by adding an alcohol compound to a metal salt or metal acid, A second step of preparing a carrier and introducing the metal precursor prepared in the first step into the carrier, A third step of adjusting the pH of a carrier into which the metal precursor obtained through the second step above has been introduced, A fourth step of generating a catalyst by heating the mixture of the metal precursor and the carrier obtained through the third step above to reduce the metal particles, A fifth step of mixing and aging the catalyst generated through the above fourth step, Step 6, which involves filtering, washing, and drying the catalyst aged through Step 5 to remove impurities, and Step 7, grinding the catalyst generated through Step 6. A method for manufacturing a metal-supported catalyst comprising 2. In Paragraph 1, A method for manufacturing a metal-supported catalyst characterized in that the metal precursor manufactured in the first step is a silver precursor.

3. In Paragraph 2, A method for manufacturing a metal-supported catalyst characterized in that the carrier used in the second step above is a carbon carrier.

4. In Paragraph 1, A method for preparing a metal-supported catalyst, characterized in that the alcohol compound used in the first step above is at least one of ethylene glycol, propylene glycol, and glycerol.

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