• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.317-322
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• 2021

Silicon (Si) has been considered as a promising anode material because of its abundant reserves in nature, low lithium ion (Li⁺) intercalation/de-intercalation potential (below 0.5 V vs. Li/Li⁺) and high theoretical capacity of 4200 mA h/g. In this paper, we prepared a silicon-based (Si-based) anode material containing a small amount of silicon carbide by using magnesiothermic coreduction of silica and hexachlorobenzene. Because of good conductivity of silicon carbide, the cycle performance of the silicon-based anode materials containing few silicon carbide is greatly improved compared with pure silicon. The raw materials were formulated according to a silicon-carbon molar ratio of 10:0, 10:1, 10:2 and 10:3, and the obtained products were purified and tested for their electrochemical properties. After 1000 cycles, the specific capacities of the materials with silicon-carbon molar ratios of 10:0, 10:1, 10:2 and 10:3 were still up to 412.3 mA h/g, 970.3 mA h/g, 875.0 mA h/g and 788.6 mA h/g, respectively. Although most of the added carbon reacted with silicon to form silicon carbide, because of the good conductivity of silicon carbide, the cycle performance of silicon-based anode materials was significantly better than that of pure silicon.

• Korean Journal of Materials Research
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• v.33 no.6
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• pp.257-264
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• 2023

To develop a high capacity lithium secondary battery, a new approach to anode material synthesis is required, capable of producing an anode that exceeds the energy density limit of a carbon-based anode. This research synthesized carbon nano silicon composites as an anode material for a secondary battery using the RF thermal plasma method, which is an ecofriendly dry synthesis method. Prior to material synthesis, a silicon raw material was mixed at 10, 20, 30, 40, and 50 wt% based on the carbon raw material in a powder form, and the temperature change inside the reaction field depending on the applied plasma power was calculated. Information about the materials in the synthesized carbon nano silicon composites were confirmed through XRD analysis, showing carbon (86.7~52.6 %), silicon (7.2~36.2 %), and silicon carbide (6.1~11.2 %). Through FE-SEM analysis, it was confirmed that the silicon bonded to carbon was distributed at sizes of 100 nm or less. The bonding shape of the silicon nano particles bonded to carbon was observed through TEM analysis. The initial electrochemical charging/discharging test for the 40 wt% silicon mixture showed excellent electrical characteristics of 1,517 mAh/g (91.9 %) and an irreversible capacity of 133 mAh/g (8.1 %).

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1296-1299
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• 2013

• Journal of Electrochemical Science and Technology
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• v.7 no.3
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• pp.228-233
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• 2016

It is hard to employ the carbon materials or the lithium metal foil for the anode of lithium sulfur batteries because of the poor passivation in ether-based electrolytes and the formation of lithium dendrites, respectively. Herein, we investigated the electrochemical characteristics of lithium sulfur batteries with lithiated silicon anode in the liquid electrolytes based on ether solvents. The silicon anodes were lithiated by direct contact with lithium foil in a 1M lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) solution in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) at a volume ratio of 1:1. They were readily lithiated up to ~40% of their theoretical capacity with a 30 min contact time. In particular, the carbon mesh reported in our previous work was employed in order to maximize the performance by capturing the dissolved polysulfide in sulfur cathode. The reversible specific capacity of the lithiated silicon-sulfur batteries with carbon mesh was 1,129 mAh/g during the first cycle, and was maintained at 297 mAh/g even after 50 cycles at 0.2 C, without any problems of poor passivation or lithium dendrite formation.

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.116-123
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• 2011

Herein, a novel preparation method of highly homogeneous carbon-silicon composite materials was presented. In contrast to conventional solvent evaporation method, a milled silicon-graphite or its oxidized material were directly reacted with petroleum-derived pitch precursor. After thermal reaction under high pressure, pitch-graphite-silicon composite was prepared. Carbon-graphite-silicon composite were prepared by an air-oxidization and following carbonization. From energy dispersive spectroscopy, it was observed that small Si particles were highly embedded within carbon, which was confirmed by disappearance of Si peaks in Raman spectra. Furthermore, X-ray diffraction and Raman spectra revealed that carbon crystallinity decreased when the strongly oxidized silicon-graphite was added, which was probably due to oxygen-induced cross-linking. From the anode application in lithium ion batteries, carbon-graphite-silicon composite anode displayed a high capacity ($565\;mAh\;g^{-1}$), a good initial efficiency (68%) and an good cyclability (88% retention at 50 cycles), which were attributed to the high dispersion of Si particles within cabon. In case of the strongly oxidized silicongraphite addtion, a decrease of reversible capacity was observed due to its low crystallinity.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.530-536
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• 2023

The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiO_x materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO₂) was synthesized using TEOS as a starting material for the fabrication of such SiO_x through heating in a reduction atmosphere. SiO_x powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiO_x powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiO_x.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.338-344
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• 2022

It is necessarily required in developing Si-based anode materials for lithium ion batteries, and the related researches are actively working especially in Si-carbon composite material. On the other hand, the photovoltaic and semiconductor industries discard huge amount of Si resources, facing the environmental issue. In this study, recycled Si resource is adopted to obtain Si-carbon composite for LIB(Lithium-Ion Batteries). In order to improve high-capacity retention characteristics and cycle stability of a Si anode material for the LIB, two differenct composites having a mass ratio of silicon and pitch of 1:1 and 2:1 are synthesized and electrochemical characteristics of the anode material manufactured by simple self-assembly method. This result in excellent initial capacity with stable cycle life, and confirming the potential use of recycled Si material for LIB.

• Journal of Power System Engineering
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• v.17 no.1
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• pp.110-115
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• 2013

The electrochemical performance and microstructure of Al-Si, Al-Si/C was investigated as anode for lithium ion battery. The Al-Si nano composite with 5 : 1 at% ratio was prepared by arc-discharge nano powder process. However, some of problem is occurred, when Al nano composite was synthesized by this manufacturing. The oxidation film is generated around Al-Si particles for passivating processing in the manufacture. The oxidation film interrupts electrical chemistry reaction during lithium ion insertion/extraction for charge and discharge. Because of the existence the oxidation film, Al-Si first cycle capacity is very lower than other examples. Therefore, carbon synthsized by glucose ($C_6H_{12}O_6$) was conducted to remove the oxidation film covered on the composite. The results showed that the first discharge cycle capacity of Al-Si/C is improved to 113mAh/g comparing with Al-Si (18.6mAh/g). Furthermore, XRD data and TEM images indicate that $Al_4C_3$ crystalline exist in Al-Si/C composite. In addition the Si-Al anode material, in which silicon is more contained was tested by same method as above, it was investigated to check the anode capacity and morphology properties in accordance with changing content of silicon, Si-Al anode has much higher initial discharge capacity(about 500mAh/g) than anode materials based on Aluminum as well as the morphology properties is also very different with the anode based Aluminum.

• Journal of Adhesion and Interface
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• v.24 no.1
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• pp.9-16
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• 2023

Silicon has been studied as an anode material for next-generation lithium ion batteries due to its high theoretical electrochemical capacity. However, the extreme volume change during the lithiation/delithiation and the inherently low electronic conductivity of silicon hamper the practical application of silicon anodes. Conductive polymer binders are effective means to solve these problems, and it has been reported that the performance of the silicon anode can be greatly improved through the proper molecular design of the conductive polymer binders. In this paper, representative recent studies on conductive polymer binders for silicon anodes will be introduced, and through this, binder design strategies to overcome the limitations of silicon anodes will be explored.

• Journal of Electrochemical Science and Technology
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• v.4 no.3
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• pp.108-112
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• 2013

Lithium diffusivity of the silicon (Si)-based materials of Si-Cu and $SiO_x$ (x = 0.4, 0.85) with improved interfacial stability to electrolyte have been determined, using variable rate cyclic voltammetry with film model electrodes. Lithium diffusivity is found to depend on the intrinsic properties of anode material and electrolyte; the fraction of oxygen for $SiO_x$ (x = 0.4, 0.85), which is directly related to electrical conductivity, and the electrolyte type with different ionic conductivity and viscosity, carbonate-based liquid electrolyte or ionic liquid-based electrolyte, affect the lithium diffusivity.