Silicon nanoparticles (Si NPs) were simply mixed with carbon nanofibers (CNFs) without any chemical process at various weight ratios, and the electrochemical properties of these nanoparticles as anode materials were investigated in lithium-ion batteries (LIBs). To study the effects of the physical incorporation of CNFs on the volumetric variations in Si NPs, the dilations of full cells were measured. The measured volumetric change of the anode using a mixture of Si NPs and CNFs was smaller than that calculated from the theoretical volumetric changes of Si and graphite. Although the reversible capacity of Si NPs faded sharply, the fading was mitigated by increasing the mixing ratio of CNFs. In particular, the Si NP/CNF mixture prepared at weight ratio retained a reversible capacity of >800 mAh/g with a capacity retention of 53.2% even after 100 cycles. CNFs alleviated stress and strain during the charge–discharge process even though there was no tight chemical bonding with Si NPs.

Silicon-carbon (Si-C) composites with various weight ratios were prepared through heat treatment of water-soluble carboxymethyl cellulose (CMC) with Si nanoparticles synthesized by using an inductively-coupled plasma. Microstructures of the Si-C composites were thoroughly investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. The results indicate that we obtained a micro-sized Si-C composite with homogeneously-distributed crystalline Si nanoparticles in an amorphous C-matrix. Pores, which were due to the volatilization of CO2 from CMC during heat treatment, was detected when the concentration of carbon was increased. The electrochemical properties of those Si-C composites for use as anode materials in lithium-ion batteries (LIBs) were also investigated. The C-matrix enhanced the capacity retention, as well as the rate capability of Si nanoparticles, due to the dense and homogeneous microstructures of the composite. The Si-C composites (7:3 weight ratio) retained a reversible capacity of > 1,000 mAh/g with a capacity retention of 88.9% even after 100 cycles. The reversible capacity ratio at a 1.5 C-rate was about 80% as compared with that at a 0.1 C-rate.

N-doped mesoporous carbon decorated TiO2 nanofibers were synthesized for the first time by a facile electrospinning process combined with subsequent heat treatment and investigated as an anode material for lithium-ion battery applications. The N-doped mesoporous carbon decorated TiO2 nanofibers had continuous one-dimensional (1-D) geometry with a smooth surface and an average thickness of ∼250 nm. The nanofibers comprised both interconnected polycrystalline TiO2 and numerous mesopores in N-doped carbon. After 100 cycles at current density of 33 mA/g, the N-doped mesoporous carbon decorated TiO2 nanofibers still exhibited a high capacity of 264 mAh/g. This superior electrochemical performance is attributed to small TiO2 crystallites, N-doped mesoporous carbon, favorable 1-D nanostructures, and smooth accommodation of the strain occurring during the charge–discharge process.

리튬이온 전지의 양극물질로써, 초임계 수열합성법을 이용해 만들어진 분말은 각각 $850^{\circ }C$와 $900^{\circ }C$ 공기 분위기에서 10시간씩 소성하여 $LiN{i}_{0.5}M{n}_{0.3}C{o}_{0.2}{O}_2$를 합성하였다. 온도를 조절함에 따라 합성된 분말은 어떠한 영향을 받는지 x-ray pattern, SEM-image, 물리적 특성과 전기화학적 거동을 관찰해 연구하였다. 그 결과, $900^{\circ }C$에서 열처리된 물질의 입자크기가 $850^{\circ }C$에서 열처리된 물질에 비해 더 큰 것으로 나타났고, 특히 초기 가역용량 163.84 mAh/g (0.1 C/2.0-4.3 V), 186.87 mAh/g (0.1 C/2.0-4.5 V)의 가역용량을 나타내면서 훌륭한 전기화학적 거동을 보였으며, 50th cycle에서도 91.49%(0.2 C/2.0-4.3 V)와 90.36%(0.2 C/2.0-4.5 V)의 높은 용량 유지율을 보였다. As the cathode material for li-ion battery, $LiN{i}_{0.5}M{n}_{0.3}C{o}_{0.2}{O}_2$ were synthesized by supercritical hydrothermal method and calcined $850^{\circ }C$ and $900^{\circ }C$ for 10hrs in air. The effect of temperature in the heat treatment on the powder and its performance were studied of xray diffraction pattern, SEM-image, physical properties and electrochemical behaviors. As a result, calcined at $900^{\circ }C$ material particle size more increase than calcined at $850^{\circ }C$ material, especially shows excellent electrochemical performance with initial reversible specific capacity of 163.84 mAh/g (0.1C/2.0-4.3V), 186.87 mAh/g (0.1C/2.0-4.5V) and good capacity retention of 91.49% (0.2C/2.0-4.3V) and 90.36% (0.2C/2.0-4.5V) after 50th charge/discharge cycle.

본 논문에서는 세그먼트 관형 고체산화물 연료전지(SOFC)의 설계 및 제작과 특성 분석을 다루고 있다. 관형 세라믹 지지체는 압출 공정을 통하여 제작하였으며, NiO-YSZ 연료극과 YSZ 전해질은 담금 코팅법을 통해 세라믹 지지체에 코팅하였다. 코팅된 세라믹 지지체를 $1,350^{\circ }C$에서 5시간 동안 열처리하였으며, $10\mu m$ 미만의 치밀하고, 균열이 없는 YSZ 전해질 층을 얻을 수 있었다. 또한 열처리된 세라믹 지지체에 LSM-YSZ/LSM/LSCF로 구성된 다층 구조 공기극을 담금법으로 코팅하여 $1,150^{\circ }C$에서 열처리하였다. 세라믹 관형 지지체에 코팅된 세그먼트 SOFC 셀은 Ag-glass 연결재를 사용하여 전기적으로 직렬 연결하였으며, 수소연료 유량과 운전 온도에 따른 세그먼트 SOFC의 성능 변화를 측정하였다. A novel design of tubular segmented-in-series(SIS) solid oxide fuel cell (SOFC) sub module was presented in this paper. The tubular ceramic support was fabricated by the extrusion technique. The NiO-YSZ anode and the yttria-stabilized zirconia (YSZ) electrolyte were deposited onto the ceramic support by dip coating method. After sintering at $1350^{\circ }C$ for 5 h, a dense and crack-free YSZ film was successfully fabricated. Also, the multi-layered cathode composed of LSM-YSZ composite, LSM and LSCF were coated onto the sintered ceramic support by dip coating method and sintered at $1150^{\circ }C$. The performance of the tubular SIS SOFC cell and sub module electrically connected by the Ag-glass interconnect was measured and analysed with different fuel flow and operating temperature.

In this study, we fabricated tubular ceramic support for segmented-in-series solid oxide fuel cell (SOFC) by using CSZ(CaO-stabilized ) as main material and activated carbon as pore former. Thermal expansion properties of ceramic support with different amounts of activated carbon were analyzed by using dilatometer to decide a suitable sintering temperature. The tubular ceramic supports with different amounts of activated carbon (5, 10, 15wt.%) were fabricated by the extrusion technique. After sintering at and for 5h., cross section and surface morphology of tubular ceramic support were analyzed by using SEM image. Also, the porosity, mechanical property, gas permeability of tubular ceramic supports was measured. Based on these results, we established the suitable fabrication technique of tubular ceramic support for segmented-in-series SOFC.

Composites of LSCF() and CGO (gadolinium doped ceria)-based ceramics are logical candidate cathode materials with CGO electrolytes. LSCF with perovskite structure was synthesized and investigated by Solid State Reaction (SSR) method used as cathode materials for SOFC (solid oxide fuel cell). The optimized temperature was to synthesize with rhombohedral structure. The polarization resistance of the LSCF/CGO (50:50 wt.%) was smaller than that of other composite cathodes. The analysis of the EIS data of LSCF/CGO suggests that the diffusion and adsorption-desorption of oxygen can be the key process in the cathodic reaction.