■ Polymer Electrolyte Membrane Fuel Cell
Polymer electrolyte membrane fuel cell is now opening up new energy industries as exampled by fuel cell electric vehicle and micro combined heat and power generation. EED lab studies micro- and nano-structural design of membrane electrode assembly with an aim to reduce the usage of expensive catalyst not losing or even enhancing durability and power performance of fuel cell. The control of interactions among ionomer, catalyst, and support expands proton-accessible active catalyst surface, and the evolution of nano-scale separation of hydrophobic and hydrophilic domains maintains air-accessible active catalyst surface even at ultra high current densities. We pursue deeper understanding on ionic and mass transport under ultra low catalyst loading and low humidity operation, and support material researchers in introducing their innovative material solutions to fuel cell devices.
Also, we attempt to elucidate the degradation mechanism at various operation modes and improve durability by physic-chemical control of membrane/catalyst layer, catalyst layer/diffusion layer, and catalyst/ionomer interface.
■ Next Generation Batteries
Li secondary battery is essential devices in human life because many electrical devices is developed and come into wide use. As the market of high energy battery for electrical vehicle and energy storage system is recently growing, next generation batteries are the good candidates to meet the demands for that. However, there are many challenges for commercialization and they have been not solved yet. We explore new battery solutions which extend cruise range of electric vehicle and provide better economics for energy storage system. Our researches include sulfur and air electrode designs with practical applicability, doughty attempt to realize lithium metal secondary batteries. We are interested in specific issues of how to realize flexible batteries with high degree of conformational freedom.
■ Redox flow batteries
Nowadays, All-Vanadium Redox Battery(VRFB), most promising Energy Storage System (EES) which is one of the in research of next-generation batteries has been widely studied in many industrial and educational research groups because of long life cycle, fast response time, environmentally friendly and the modularity of their energy & power capacity which are independent of each other. However, due to several problems about stability of electrolyte and energy efficiency, there have been numerous efforts to overcome limits of narrow operating temperature and fastidious condition that VRFB needs to operate. In this regard, our group introduces some development related to ion-exchange membrane, improved electrolyte and mechanism model that play an important role of research key point of VRFB. In addition, we also attempt to suggest operating technique to drive VRFB efficiently.
■ Micro/nano structure fabrication by using photo-reactive materials
Progress toward the fabrication of tailor made micro/nano structures is of paramount importance in the fields such as photonics, surface science, biotechnology, and electronics. In line with this, our group developed a novel micro/nano structure fabrication technique, named as the directional photofluidization lithography (DPL). The key of DPL is of using photo-reactive materials such as azobenzene molecular incorporated in polymer, glass, inorganic precursor, or dendrimer. Such photo-reactive materials enable the anisotropic movement along with polarization of irradiation light. By utilizing this peculiar phenomenon, the pre-fabricated structures can be reshaped into various forms (from high-resolution size to sophisticated shape). Moreover, DPL enables scalable, parallel, and cost-effective processing, where the previous nanofabrication techniques are difficult to achieve. In this stage, we are investigating the use of fabricated pattern into real devices applications. We also study the combination work of DPL with other conventional lithographic technique for fabricating unprecedented complex 2D and 3D patterned structure.
■ Flexible Electronics
The flexible electronics is the technology for assembling electronics on the flexible plastic substrates. The main beauty of this technology is the flexibility, lightweight, and durability. The examples are including flexible electronic circuits, flexible display, flexible solar cell, and flexible touch screen. Recently, our group firstly demonstrated flexible and light-powered healable electrical conductor. This work showed that the light even with relatively low intensity can provide repetitive recovery of a damaged flexible electrical conductive pathway without any direct invasion and within a few minutes. Our group is also focused on developing a transparent and flexible electrode by using silver nanowires. We are investigating the prepared electrode to be exploited in various optoelectronic devices including touch penal, solar cell, and light emitting diode.
Hee Tak Kim (김희탁)