Silicon-carbon composite manufacturing method, silicon-carbon composite manufactured thereby, and lithium secondary battery containing the same

Abstract

A method for manufacturing a silicon-carbon composite is provided, comprising the steps of: impregnating graphite into a mixed solution containing a silicon precursor, APTES (Amino Propyl Tri Ethoxy Silane), and toluene; ultrasonically treating the solution containing the graphite; obtaining powder from the ultrasonically treated solution and then drying it; and heat-treating the dried powder.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a silicon-carbon composite, a silicon-carbon composite manufactured thereby, and a lithium secondary battery comprising the same. Background Technology

[0002] Recently, due to the advancement of small electronic devices such as mobile terminals and the growth of the electric vehicle and energy storage industries, there is a significant demand for the development of high-capacity lithium-ion batteries. In response to these market demands, the high performance of secondary batteries used as power sources has become a major focus. Among secondary battery systems, numerous studies are being reported on lithium-ion batteries, which offer the advantages of miniaturization, high energy density, and long cycle life.

[0003] Lithium secondary batteries consist of a cathode, anode, electrolyte, and separator, and can be manufactured in various forms depending on the type of each material; among these, the anode significantly affects the capacity and lifespan characteristics of the lithium secondary battery.

[0004] Currently, carbon-based materials including graphite are mainly used as cathode materials. While commercially available graphite has the advantages of having low volume change and being cost-effective, there is a need for the development of new cathode materials with high capacity characteristics due to the disadvantage of having a low theoretical capacity of 372 mAh / g.

[0005] Recently, silicon (Si), tin (Sn), germanium (Ge), and magnesium (Mg), which form alloys with lithium, are attracting attention as materials that can replace graphite. In particular, silicon has a very high theoretical capacity of 4200 mAh / g, and research to utilize it is actively underway due to the advantage of achieving about 11 times the capacity of graphite.

[0006] The reaction equation when lithium is inserted into silicon is as follows.

[0007] 22Li + 5Si = Li22 Si5

[0009] However, silicon has the disadvantage of undergoing volume expansion and contraction of more than 300% when forming an alloy with lithium during charging and discharging. This leads to the pulverization of silicon particles, as well as electrode detachment and cracking, resulting in electrode damage and increased electrode resistance. Additionally, as charge-discharge cycles progress, irreversible capacity loss increases, causing a decrease in battery capacity.

[0010] To address these issues, research is being conducted to minimize internal stress in electrodes and improve electrode lifespan characteristics by utilizing silicon with particle size and porous structure, or silicon oxide, to buffer volume changes occurring during the charging and discharging process. Additionally, studies have been reported on forming silicon-carbon nanocomposites using carbon-based nanomaterials such as CNTs and graphene to buffer volume expansion and reduce irreversible capacity loss.

[0011] However, such silicon shape control and composite formation technologies require high process costs and complex technical expertise. Therefore, there is a need to develop manufacturing methods that utilize silicon as anode materials to increase the capacity of lithium-ion batteries, reduce process costs, and enable mass production with relatively simple technology. Prior art literature

[0012] 1. Republic of Korea Published Patent 10-2023-01150322. Republic of Korea Registered Patent 10-25313903. Republic of Korea Registered Patent 10-2377106 The problem to be solved

[0013] Therefore, the problem that the present invention aims to solve is to provide a method and material that utilize silicon in the negative electrode material to increase the capacity of lithium secondary batteries, can lower process costs, and enables mass production with relatively simple technology. means of solving the problem

[0014] To solve the above problem, the present invention provides a method for manufacturing a silicon-carbon composite comprising the steps of: impregnating graphite into a mixed solution containing a silicon precursor, which is APTES (Amino Propyl Tri Ethoxy Silane), and toluene; ultrasonically treating the solution containing the graphite; obtaining powder from the ultrasonically treated solution and then drying it; and heat-treating the dried powder.

[0015] In one embodiment of the present invention, the volume ratio of the silicon precursor and toluene in the mixed solution is 90:10.

[0016] In one embodiment of the present invention, the heat treatment is performed in an argon and hydrogen atmosphere.

[0017] In one embodiment of the present invention, the ultrasonic treatment is performed for 60 minutes or more.

[0018] In one embodiment of the present invention, the heat treatment is performed at a temperature of 400 to 800°C.

[0019] The present invention also provides a silicon-carbon composite manufactured by the silicon-carbon composite manufacturing method described above.

[0020] In one embodiment of the present invention, the silicon content of the silicon-carbon composite is 8 weight% or more.

[0021] In one embodiment of the present invention, the silicon content is controlled by any one of the heat treatment temperature, the volume ratio of the silicon precursor and toluene, and the ultrasonic treatment time.

[0022] The present invention also provides an electrode comprising the silicon-carbon composite described above.

[0023] In one embodiment of the present invention, the electrode is the negative electrode of a lithium secondary battery.

[0024] The present invention also provides a lithium secondary battery comprising the electrode described above. Effects of the invention

[0025] According to the present invention, a method is provided for manufacturing a composite material composed of silicon oxide and graphite by impregnating graphite into a silicon liquid precursor and then performing a simple heat treatment process. In particular, the present invention enables the production of a composite material with desired characteristics by controlling process variables such as the heat treatment temperature and the solution composition ratio. Accordingly, by utilizing the silicon oxide-graphite composite material manufactured by the method according to the present invention as a negative electrode active material for a lithium secondary battery, a lithium secondary battery having high capacity and long lifespan characteristics can be provided. Brief explanation of the drawing

[0026] FIG. 1 is a method for manufacturing a silicon-carbon composite according to one embodiment of the present invention, and FIG. 2 is a schematic diagram of a process for manufacturing a silicon-carbon composite according to one embodiment of the present invention. Figure 3 shows an SEM image, Raman spectrum, and XRD analysis results of graphite, which is the material before manufacturing the composite material according to one embodiment of the present invention. Figure 4 shows the SEM image, Raman spectrum, EDS, and XRD analysis results of a silicon-graphite composite material prepared according to one embodiment of the present invention ((graphite : APTES = 0.5 g : 20 mL, APTES : toluene = 90 : 10 vol.%, heat treatment at 800℃ for 10 minutes, ultrasonic treatment for 60 minutes) Figure 5 shows the SEM, EDS, and Raman analysis results of silicon-graphite composite materials prepared with different mixing ratios of APTES and toluene (graphite : APTES = 0.5 g : 20 mL, heat treatment at 800 °C for 10 minutes, ultrasonic treatment for 60 minutes). Figure 6 shows the SEM, EDS, and Raman analysis results of silicon-graphite composite materials prepared according to heat treatment temperature (graphite : APTES = 0.5 g : 20 mL, APTES : toluene = 90 : 10 vol.%, ultrasound 60 min). Figure 7 shows the SEM, EDS, and Raman analysis results of silicon-graphite composite materials prepared according to ultrasonic treatment time (graphite : APTES = 0.5 g : 20 mL, APTES : toluene = 90 : 10 vol.%, heat treated at 800℃ for 10 minutes). Figure 8 shows the TGA analysis results of silicon oxide-graphite composite materials prepared according to heat treatment conditions. Specific details for implementing the invention

[0027] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0028] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this invention, terms such as "comprising" or "having" are intended to indicate the presence of the features, numbers, steps, actions, components, parts, 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, parts, or combinations thereof.

[0029] To solve the aforementioned problem, the present invention provides a method for manufacturing a composite material composed of silicon oxide and graphite by impregnating graphite into a silicon liquid precursor and then performing a simple heat treatment process. By utilizing the silicon oxide-graphite composite material manufactured by the method according to the present invention as a negative electrode active material for a lithium secondary battery, a lithium secondary battery having high capacity and long lifespan characteristics can be provided.

[0030] In addition, graphite powder [95% purity, <20 μm powder (Sigma Aldrich)] consists of particles with a diameter of tens of micrometers and does not require a separate pretreatment process.

[0032] Hereinafter, a detailed description of the present invention is provided with reference to the accompanying drawings. Embodiments of the present invention may be modified in various different forms, and this implies that the scope of the present invention is not limited to the embodiments described below. Accordingly, the size and shape of the elements shown in the accompanying drawings may be exaggerated for clearer explanation and should be interpreted to define the technical aspects of the present invention.

[0034] Examples

[0035] FIG. 1 is a method for manufacturing a silicon-carbon composite according to one embodiment of the present invention, and FIG. 2 is a schematic diagram of a process for manufacturing a silicon-carbon composite according to one embodiment of the present invention.

[0036] Referring to FIGS. 1 and 2, in one embodiment of the present invention, APTES (Amino Propyl Tri Ethoxy Silane) was mixed with toluene as a silicon precursor to prepare a mixed solution. Subsequently, graphite powder was impregnated into the mixed solution, composited through an ultrasonic treatment process, dried at 150°C for 10 minutes, heat-treated in an argon and hydrogen atmosphere, and then air-cooled to room temperature while flowing Ar gas at 950 sccm to produce a silicon-carbon composite material composed of silicon oxide and graphite.

[0037] At this time, a solution was prepared by mixing APTES solution with toluene, and the concentrations were varied at 10:90, 50:50, and 90:10 vol.%. After mixing the solution with graphite powder, an ultrasonic treatment process was carried out at different treatment times of 10, 30, and 60 minutes. In addition, the heat treatment process was carried out at different heat treatment temperatures of 600, 800, and 1000 ℃, and heat treatment was performed for 10 minutes under atmospheric pressure while flowing a mixed gas of Ar and H2 (900:100 sccm).

[0039] Experimental Example

[0040] Figure 3 shows an SEM image, Raman spectrum, and XRD analysis results of graphite, which is the material before manufacturing the composite material according to one embodiment of the present invention.

[0041] Referring to FIG. 3, it can be seen that the graphite, which is the material used in the process according to one embodiment of the present invention, is a particle having a diameter of several tens of micrometers.

[0042] Figure 4 shows the SEM image, Raman spectrum, EDS, and XRD analysis results of a silicon-graphite composite material prepared according to one embodiment of the present invention ((graphite : APTES = 0.5 g : 20 mL, APTES : toluene = 90 : 10 vol.%, heat treatment at 800℃ for 10 minutes, ultrasonic treatment for 60 minutes)

[0043] Referring to Figure 4, there was no change in the shape of the graphite particles when compared to the graphite particles before manufacturing, and the EDS analysis results showed that the spatial positions of carbon and silicon present in the graphite particles matched, confirming that the silicon-graphite composite material was well formed.

[0044] In addition, based on the observation of predominantly graphite peaks in Raman analysis and predominantly silicon oxide peaks in XRD analysis, it is determined that a silicon-graphite composite material has been formed.

[0045] Figure 5 shows the SEM, EDS, and Raman analysis results of silicon-graphite composite materials prepared with different mixing ratios of APTES and toluene (graphite : APTES = 0.5 g : 20 mL, heat treatment at 800 °C for 10 minutes, ultrasonic treatment for 60 minutes).

[0046] Referring to Figure 5, it can be seen that the weight percentage of silicon increases as the volume ratio of APTES increases. That is, as the volume ratio of APTES increases, the weight of silicon increases, which is the same as Figure 6 below. In addition, the increased silicon content of the composite material was maintained at approximately 8 wt% even after heat treatment at 800°C for 10 minutes, and Raman analysis results showed the best crystallinity under the condition of “APTES:toluene = 90:10 vol.%” (ID / IG = 0.32). Therefore, it can be seen that impregnating with an APTES:toluene = 90:10 vol.% solution is desirable to maintain high silicon content and excellent graphite crystallinity.

[0047] Figure 6 shows the SEM, EDS, and Raman analysis results of silicon-graphite composite materials prepared according to heat treatment temperature (graphite : APTES = 0.5 g : 20 mL, APTES : toluene = 90 : 10 vol.%, ultrasound 60 min).

[0048] Referring to Fig. 6, it can be seen that the weight percentage of silicon is highest when the heat treatment temperature is 600°C. Therefore, in order to maintain appropriate silicon content conditions, it is desirable to perform heat treatment at a temperature of 400 to 800°C, and most preferably at 550 to 700°C, which maintains a silicon content of 8% or more by weight.

[0049] Figure 7 shows the SEM, EDS, and Raman analysis results of silicon-graphite composite materials prepared according to ultrasonic treatment time (graphite : APTES = 0.5 g : 20 mL, APTES : toluene = 90 : 10 vol.%, heat treated at 800℃ for 10 minutes).

[0050] Referring to Fig. 7, it can be seen that the silicon content is maintained at a level of 8 wt% for more than 60 minutes.

[0051] Figure 8 shows the TGA analysis results of silicon oxide-graphite composite materials prepared according to heat treatment conditions.

[0052] Referring to Figure 8, when comparing the conditions before impregnation, after impregnation, and after impregnation / heat treatment, the sample without heat treatment showed a high weight loss rate, which is judged to be the result of all physically adsorbed APTES evaporating during the heat treatment process. Therefore, it is judged that a heat treatment process is essential for manufacturing silicon-graphite composite materials, and that even after the heat treatment process, a silicon-graphite composite material with thermal stability is well formed and its weight is maintained.

[0054] As described above, the present invention provides a method for manufacturing a composite material composed of silicon oxide and graphite by impregnating graphite into a mixed solution containing a silicon liquid precursor and then performing a simple heat treatment process. In particular, the silicon content in the composite of the present invention can be controlled by any one of the heat treatment temperature, the volume ratio of the silicon precursor and toluene, and the ultrasonic treatment time. Accordingly, by using the silicon oxide-graphite composite material manufactured by the method according to the present invention as a negative electrode active material for a lithium secondary battery, a lithium secondary battery having high capacity and long life characteristics can be provided.

Claims

Claim 1 A method for manufacturing a silicon-carbon composite comprising: a step of impregnating graphite into a mixed solution containing a silicon precursor, which is APTES (Amino Propyl Tri Ethoxy Silane), and toluene; a step of ultrasonically treating the solution impregnated with graphite; a step of obtaining a powder from the ultrasonically treated solution and then drying it; and a step of heat-treating the dried powder, wherein the volume ratio of the silicon precursor and toluene in the mixed solution is 90:

10. Claim 2 delete Claim 3 A method for manufacturing a silicon-carbon composite according to claim 1, wherein the heat treatment is performed in an argon and hydrogen atmosphere. Claim 4 A method for manufacturing a silicon-carbon composite according to claim 1, characterized in that the ultrasonic treatment is performed for 60 minutes or more. Claim 5 A method for manufacturing a silicon-carbon composite according to claim 1, characterized in that the heat treatment is performed at a temperature of 400 to 800℃. Claim 6 A silicon-carbon composite manufactured by a method for manufacturing a silicon-carbon composite according to any one of claims 1, 3 to 5, wherein the silicon content of the silicon-carbon composite is 8 weight% or more. Claim 7 delete Claim 8 A silicon-carbon composite according to claim 6, characterized in that the silicon content is controlled by any one of the heat treatment temperature, the volume ratio of silicon precursor and toluene, and the ultrasonic treatment time. Claim 9 An electrode comprising a silicon-carbon composite according to claim 6. Claim 10 An electrode according to claim 9, characterized in that the electrode is a negative electrode of a lithium secondary battery. Claim 11 A lithium secondary battery comprising an electrode according to claim 9.

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