The single-step co-firing technique was developed from the tape-casting/ lamination/co-firing process to fabricate solid oxide fuel cells (SOFCs) cost-effectively. The anode and cathode consisted with nano-composite powders were optimized to improve the performance and the durability of the unit cel...
The single-step co-firing technique was developed from the tape-casting/ lamination/co-firing process to fabricate solid oxide fuel cells (SOFCs) cost-effectively. The anode and cathode consisted with nano-composite powders were optimized to improve the performance and the durability of the unit cells. The catalysts and operating conditions for suppressing the carbon deposition occurred during direct utilization of methane fuel, which were also optimized to demonstrate the high-performance and durable methane-fueled SOFCs The basic Ni-YSZ anode supported unit cells {Ni-YSZ anode // YSZ electrolyte // LSM-YSZ cathode (Ф = 2.6 cm)} were manufactured by laminating 100㎛-thick Ni-YSZ anodes and 10㎛-thick YSZ electrolytes prepared via tape-casting followed by burn-out and co-firing of the laminate at 1350 oC, screen-printing the LSM-YSZ cathode on the YSZ electrolyte and firing at 1150oC. These unit cells yielded a high power density of 0.75 W/cm2, 0.5 W/cm2, and 0.4 W/cm2 at 800 oC, 700 oC, and 650 oC, respectively with 30cc/min, 25cc/min, and 20 cc/min of methane flow rate. The most optimal methane flow rate was 25cc/min at 700 oC for stable long-term operation, which resulted from the utilization of some useful deposited carbon as fuels and the minimization of the carbon deposition rate. The 1wt% Li2TiO3 catalyst-doped Ni based anode supported unit cells were developed to prevent carbon deposition, which showed 0.4 W/cm2 and over 50 hour-stability at 800 oC, although an 100cc/min of excess methane flow rate was supplied. The reason why these unit cells showed a lower power density than non catalyst-doped unit cells is the Li2TiO3 catalyst played as sintering aid that reduces the porosity and the active site of an anode. The high oxygen ionic conductor GDC electrolyte and NiO/GDC-GDC dual nano-composite powder with nano-sized Ni and GDC coating on a core GDC particle was synthesized by the Pechini Process, which were used to improve the cell performance of the intermediate temperature-SOFCs. The Ni/GDC-GDC anode supported unit cells (Ni/GDC-GDC dual nano-composite anode // GDC electrolyte //LSCF-GDC cathode) were fabricated by the same tape-casting /lamination procedure as above, and firing a screen-printed LSCF-GDC cathode at 1000 oC after the co-firing the anode supported electrolyte at 1400 oC. This unit cell yielded a high 0.75 W/cm2 of maximum power density and 73 % of methane utilization with 500 hour-stability with CH4 at 650 oC. The SnO2 catalyst effects suppression of the carbon deposition from the methane pyrolysis reaction, and the maintenance of anode microstructure. The SnNi/GDC-GDC anode supported unit cells showed the improved maximum power density and fuel utilization as 0.93 W/cm2 and 80 %. Ni/GDC-GDC unit cells were scaled up to 5x5 cm2 size, its flatness was optimized to 55㎛/5cm by applying 11.3 g/cm2 load during co-firing, and its 9.6 W power was evaluated in the parallel flow path housing. However, it was found that the performances of unit cell and carbon deposition were selectively changed depending on the material and flow path of housing. The monolithic anode-supported unit cells consisted with an anode, an electrolyte and cathode, were cost-effectively fabricated with tape-casting/lamination and single-step co-firing processes. The monolithic unit cells (Ni/YSZ-YSZ nano-composite anode // YSZ electrolyte // LSM/GDC nano-composite cathode) showed 0.81 W/cm2 of maximum power density, which were fabricated by optimizing the single-step co-firing temperature via the analysis of YSZ sinterability, and Ni/YSZ-YSZ and LSM/GDC nano-composite electrodes have a high porosity and a low area specific resistance at high temperature. In the future, it is expected that the single-step co-firing technique can be applied as a manufacturing process for the commercialization of solid oxide fuel cells as a high efficiency and practical process.
The single-step co-firing technique was developed from the tape-casting/ lamination/co-firing process to fabricate solid oxide fuel cells (SOFCs) cost-effectively. The anode and cathode consisted with nano-composite powders were optimized to improve the performance and the durability of the unit cells. The catalysts and operating conditions for suppressing the carbon deposition occurred during direct utilization of methane fuel, which were also optimized to demonstrate the high-performance and durable methane-fueled SOFCs The basic Ni-YSZ anode supported unit cells {Ni-YSZ anode // YSZ electrolyte // LSM-YSZ cathode (Ф = 2.6 cm)} were manufactured by laminating 100㎛-thick Ni-YSZ anodes and 10㎛-thick YSZ electrolytes prepared via tape-casting followed by burn-out and co-firing of the laminate at 1350 oC, screen-printing the LSM-YSZ cathode on the YSZ electrolyte and firing at 1150oC. These unit cells yielded a high power density of 0.75 W/cm2, 0.5 W/cm2, and 0.4 W/cm2 at 800 oC, 700 oC, and 650 oC, respectively with 30cc/min, 25cc/min, and 20 cc/min of methane flow rate. The most optimal methane flow rate was 25cc/min at 700 oC for stable long-term operation, which resulted from the utilization of some useful deposited carbon as fuels and the minimization of the carbon deposition rate. The 1wt% Li2TiO3 catalyst-doped Ni based anode supported unit cells were developed to prevent carbon deposition, which showed 0.4 W/cm2 and over 50 hour-stability at 800 oC, although an 100cc/min of excess methane flow rate was supplied. The reason why these unit cells showed a lower power density than non catalyst-doped unit cells is the Li2TiO3 catalyst played as sintering aid that reduces the porosity and the active site of an anode. The high oxygen ionic conductor GDC electrolyte and NiO/GDC-GDC dual nano-composite powder with nano-sized Ni and GDC coating on a core GDC particle was synthesized by the Pechini Process, which were used to improve the cell performance of the intermediate temperature-SOFCs. The Ni/GDC-GDC anode supported unit cells (Ni/GDC-GDC dual nano-composite anode // GDC electrolyte //LSCF-GDC cathode) were fabricated by the same tape-casting /lamination procedure as above, and firing a screen-printed LSCF-GDC cathode at 1000 oC after the co-firing the anode supported electrolyte at 1400 oC. This unit cell yielded a high 0.75 W/cm2 of maximum power density and 73 % of methane utilization with 500 hour-stability with CH4 at 650 oC. The SnO2 catalyst effects suppression of the carbon deposition from the methane pyrolysis reaction, and the maintenance of anode microstructure. The SnNi/GDC-GDC anode supported unit cells showed the improved maximum power density and fuel utilization as 0.93 W/cm2 and 80 %. Ni/GDC-GDC unit cells were scaled up to 5x5 cm2 size, its flatness was optimized to 55㎛/5cm by applying 11.3 g/cm2 load during co-firing, and its 9.6 W power was evaluated in the parallel flow path housing. However, it was found that the performances of unit cell and carbon deposition were selectively changed depending on the material and flow path of housing. The monolithic anode-supported unit cells consisted with an anode, an electrolyte and cathode, were cost-effectively fabricated with tape-casting/lamination and single-step co-firing processes. The monolithic unit cells (Ni/YSZ-YSZ nano-composite anode // YSZ electrolyte // LSM/GDC nano-composite cathode) showed 0.81 W/cm2 of maximum power density, which were fabricated by optimizing the single-step co-firing temperature via the analysis of YSZ sinterability, and Ni/YSZ-YSZ and LSM/GDC nano-composite electrodes have a high porosity and a low area specific resistance at high temperature. In the future, it is expected that the single-step co-firing technique can be applied as a manufacturing process for the commercialization of solid oxide fuel cells as a high efficiency and practical process.
Keyword
#고체산화물 연료전지 테이프캐스팅 적층 동시소성 일체형 단위전지 평탄도 나노복합 분말 solid oxide fuel cell (SOFC) tape-casting lamination co-firing monolithic unit cell flatness nano-composite powder
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