Hyung-Tae Lim

Single-step Preparation of Nano-homogeneous NiO/YSZ Composite Anode for Solid Oxide Fuel Cells

Homogeneous co-precipitation and hydrothermal treatment were used to prepare nano- and highly dispersed NiO/YSZ (yttria-stabilized zirconia) composite powders. Composite powders of size less than 100 nm were successfully prepared. This process did not require separate sintering of the YSZ and NiO to be used as the raw materials for solid oxide fuel cells. The performance of a cell fabricated using the new powders (max. power density ∼0.87 W/cm2) was higher than that of a cell fabricated using conventional powders (max. power density ∼0.73 W/cm2). Co-precipitation and hydrothermal treatment proved to be very effective processes for reducing cell production costs as well as improving cell performance.

Anode performance of lithium–silicon alloy prepared by mechanical alloying for use in all-solid-state lithium secondary batteries

Li22Si5 alloy powder was synthesized by mechanical alloying and its electrochemical performance was investigated for use in solid-state battery anodes. Two types of anode powder were prepared: 1) Li–Si alloy powder after mechanical alloying with Li-granules and Si-powder, and 2) Li–Si alloy powder from the first process followed by additional ball milling for reduction of particle size. Using these anode materials, all-solid-state lithium batteries were assembled with Li4Ti5O12 (LTO) as cathode and Li2S–P2S5 as electrolyte. Impedance spectra of the two types of cells were measured, and the results showed that the non-ohmic resistance was less in the case of the cell with the secondary ball-milled, fine anode powder. Galvanostatic charge/discharge tests were also performed, and capacity was increased about two times by the additional powder milling process; which is consistent with the impedance results. Thus, the results from the present work indicate that using the secondary milling process to refine the electrode powder is an effective way to increase the kinetics of alloying and de-alloying with improvement in interfacial properties in all-solid-state lithium secondary batteries.

Solid Oxide Fuel Cell Materials

Solid oxide fuel cells (SOFCs) are promising power generation systems that electrochemically convert chemical energy into electrical energy with little or no emission of pollutants [1–3]. Moreover, a high-temperature fuel cell has many advantages such as a high efficiency and fuel flexibility in comparison with a low-temperature fuel cell. For these reasons, a considerable amount of attention has been paid to SOFCs in recent years for application to medium- to large-scale power generation and combined heat and power (CHP).

Enhanced electrochemical performance of surface-treated Li[Ni0.8Co0.1Mn0.1]O2 cathode material for lithium-ion batteries

In order to enhance the electrochemical performance of the Li[Ni_0.8Co_0.1Mn_0.1]O₂ cathode material synthesized using co-precipitation, its surface was coated with Al₂O₃ by using atomic layer deposition. The crystal structure of the bare and coated material was analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The material showed a layered structure and no impurity phase. No change in the crystal structure was observed after surface coating. The synthesized particles were spherical, with an approximate size of 5-20 μm. The prepared Li[Ni_0.8Co_0.1Mn_0.1]O₂ showed a fairly high discharge capacity of 241.8 mAh/g. After being coated with 3 nm of Al₂O₃, the electrochemical properties were enhanced, together with the charge/discharge cycling properties at room and elevated temperatures.