• 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.

• Particle and aerosol research
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• v.15 no.4
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• pp.127-137
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• 2019

Recently, high electrochemical performance anode materials for lithium ion secondary batteries are of interest. Here, we present silicon-carbon-graphene (Si-C-GR) composites for high performance anode materials of lithium ion secondary battery (LIB). Aerosol process and heat-treatment were employed to prepare the Si-C-GR composites using a colloidal mixture of silicon, glucose, and graphene oxide precursor. The effects of the size of the silicon particles in Si-C-GR composites on the material properties including the morphology and crystal structure were investigated. Silicon particles ranged from 50 nm to 1 ㎛ in average diameter were employed while concentration of silicon, graphene oxide and glucose was fixed in the aerosol precursor. Morphology of as-fabricated Si-C-GR composites was generally the shape of a crumpled paper ball and the Si particles were well wrapped in carbon and graphene. The size range of composites was about from 2.2 to 2.9 ㎛. The composites including silicon particles larger than 200 nm in size exhibited higher performance as LIB anodes such as capacity and coulombic efficiency than silicon particles less than 100 nm, which were about 1500 mAh/g at 100 cycles in capacity and 99% in coulombic efficiency, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.353-363
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• 2012

The relationship between the diffusivity and electrochemical characteristics of lithium secondary battery with the modified Si anode material prepared in HF/$AgNO_3$ solution was investigated. The crystallographic structure and images of the modified porous Si and modified Si/Cu was examined using the X-ray diffraction, BET and SEM. To examine the effect of metal composite and pore size distribution according to chemical etching on the electrochemical characterization, the electrodes for half cells were prepared with the modified Si, modified Si/Cu, and modified Si/Cu annealed with $600^{\circ}C$. Our results showed that the chemical diffusivity of lithium ions was related to structure and resistance of Si/Cu composite anode material. The lithium diffusivity in modified silicon compound calculated from the CV was at the range of $1{\times}10^{-12}$ to $9{\times}10^{-16}cm^2/s$. The effects of modified silicon structure and resistance on the cycling efficiency were significant.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.118-123
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• 2019

In this study, the electrochemical characteristics of Graphite/Silicon/Pitch anode composites were analyzed to improve the low theoretical capacity of graphite as a lithium ion battery. The Graphite/Silica composites were synthesized by bonding silica onto polyvinylpyrrolidone coated graphite. The surface of used silica was treated with (3-Aminopropyl)triethoxysilane(APTES). Graphite/Silicon/Pitch composites were prepared by carbonization of petroleum pitch, the fabrication processes including the magnesiothermic reduction of nano silica to obtain silicon and varying the mass ratio of silica. The Graphite/Silicon/Pitch composites were analysed by XRD, SEM and XRD. Also the electrochemical performances of Graphite/Silicon/Pitch composite as the anode of lithium ion battery were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance tests in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC:DMC:EMC=1:1:1 vol%). The Graphite/Silicon/Pitch anode composite (silica 28.5 in weight) has better capacity (537 mAh/g). The cycle performance has an excellent capacity retention to 30th cycle of 95% and the retention rate capability of 98% in 0.1 C/0.2 C.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.262-268
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• 2024

In this study, the MXene/Si composite was prepared by electrostacic assembly with 2-dimensional structured titanium carbide (MXene) and nano silicon for anode material of high-performance lithium-ion battery. Ti₃C₂T_x MXene was synthesized by etching the Ti₃AlC₂ MAX with LiF/HCl, and the surface of nano silicon was charged to positively using CTAB (Cetyltrimethylammonium bromide). The MXene/Si anode composite was successfully manufactured by simple mixing process of synthesized MXene and charged silicon. The physical and electrochemical properties of prepared composite were investigated with MXene-silicon composition ratio, and the surface of electrode after cycles was analyzed to evaluate stability of the electrode. The MXene/Si composites demonstrated high initial discharge capacities of 1962.9, 2395.2 and 2504.3 mAh/g as the silicon composition ratio increased to 2, 3 and 4 compared to MXene, respectively. MXene/Si-4, which is MXene and silicon ratio with 1 : 4, exhibited 1387.5 mAh/g of reversible capacity, 74.5% of capacity retention at 100 cycles and high capacity of 700.5 mAh/g at high rate of 4.0 C. As the results, the MXene/Si composite prepared by electrostatic-assenbly could be applied to anode materials for high-performance LIBs.

• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.112-121
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• 2019

In this study, silicon / carbon nanotube / carbon composite particles with high capacity were fabricated by using micro-sized silicon particles and carbon nanotubes as an anode material for lithium ion batteries. The silicon / carbon nanotube / carbon composite particles were prepared by spray drying method to prepare spherical composite particles. The composite particles have the network structure of the carbon nanotubes around the silicon particles, in which the silicon particles and the carbon nanotubes are bonded by amorphous carbon. It appears that the volume expansion of silicon is effectively buffered and the electrical contact is maintained in the network structure of the composite particles during charge-discharge cycles.

• 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.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.303-308
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• 2018

Silicon/Carbon (Si/C) composite as anode materials for lithium-ion batteries was synthesized to find the effect of binders and an electrolyte additive. Si/C composites were prepared by two step method, including magnesiothermic reduction of SBA-15 (Santa Barbara Amorphous material No. 15) and carbonization of phenol resin. The electrochemical performances of Si/C composites were investigated by charge/discharge, cyclic voltammetry and impedance tests. The anode electrode of Si/C composite with PAA binder appeared better capacity (1,899 mAh/g) and the capacity retention ratio (92%) than that of other composition coin cells during 40 cycles. Then, Vinylene carbonate (VC) was tested as an electrolyte additive. The influence of this additive on the behavior of Si/C anodes was very positive (3,049 mAh/g), since the VC additive is formed passivation films on Si/C surfaces and suppresses irreversible changes.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.3025-3032
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• 2012

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a two step polymerization method. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were prepared with a wet-type beadsmill method. A polymer, which is easily removable by a thermal treatment (intermediate polymer) was polymerized on the outer surfaces of Si-CNT nanocomposites. Subsequently, another polymer, which can be carbonized by thermal heating (carbon precursor polymer) was incorporated onto the surfaces of pre-existing polymer layer. In this way, polymer precursor spheres containing Si-CNT nanohybrids were produced using a two step polymerization. The intermediate polymer must disappear during carbonization resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.32-38
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• 2023

In this study, the electrochemical properties of dopamine coated silicon/silicon carbide/carbon(Si/SiC/C) composite materials were investigated to improve cycle stability and rate performance of silicon-based anode active material for lithium-ion batteries. After synthesizing CTAB/SiO₂ using the Stöber method, the Si/SiC composites were prepared through the magnesium thermal reduction method with NaCl as heat absorbent. Then, carbon coated Si/SiC anode materials were synthesized through polymerization of dopamine. The physical properties of the prepared Si/SiC/C anode materials were analyzed by SEM, TEM, XRD and BET. Also the electrochemical performance were investigated by cycle stability, rate performance, cyclic voltammetry and EIS test of lithium-ion batteries in 1 M LiPF₆ (EC: DEC = 1:1 vol%) electrolyte. The prepared 1-Si/SiC showed a discharge capacity of 633 mAh/g and 1-Si/SiC/C had a discharge capacity of 877 mAh/g at 0.1 C after 100 cycles. Therefore, it was confirmed that cycle stability was improved through dopamine coating. In addition, the anode materials were obtain a high capacity of 576 mAh/g at 5 C and a capacity recovery of 99.9% at 0.1 C/0.1 C.