Cheol-Woo Yi

The Synthesis and Electrochemical Properties of Lithium Manganese Oxide (Li 2 MnO 3 )

The layered lithium-manganese oxide () as a cathode material of lithium ion secondary batteries was prepared and characterized the physico-chemical and electrochemical properties. The morphological and structural changes of MnO(OH) and are closely connected to the changes of electrochemical properties. The crystallinity of is enhanced as the annealing temperature increase, but its capacity is reduced due to the easier structural changes of less crystalline than highly crystalline one. Moreover, the addition of buffer material such as MnO(OH) into cathode causes to reduce the morphological and structural changes of layered and increase the discharge capacity and cycleability.

The Stable Rechargeability of Secondary Zn-Air Batteries: Is It Possible to Recharge a Zn-Air Battery?

Department of Chemistry and Institute of Basic Science, Sungshin Women’s University, Seoul 136-742, South Korea(Received January 28, 2010 : Accepted February 11, 2010)Abstract : The rechargeable Zn-air battery is considered as one of the potential candidates for thenext generation secondary batteries due to its many advantages. However, its further applicationsand commercialization have been limited by the complexity of the reactions on air electrodewhich are oxygen reduction and evolution reactions (ORR/OER) upon discharging and chargingprocesses, respectively. In the present study, lanthanum was impregnated into a commercial Pt/Cgas diffusion electrode, and it clearly verified significantly enhanced cycling stability and revers-ibility. The results presented in this study show the possibility of repeated charge/discharge processesfor Zn-air batteries with a La-loaded air electrode, and they demonstrate the potential as a prom-ising next generation secondary battery.Keywords : Secondary battery, Zn-air battery, Rechargeable, Oxygen evolution reaction, Oxygenreduction reaction

Spectrophotometric study of the corrosion behaviour of chromium in molten alkali carbonates

Abstract The corrosion of chromium species in molten (Li/K) 2 CO 3 and (Li/Na/K) 2 CO 3 are investigated by spectrophotometry. A strong charge-transfer absorption band is observed in the ultraviolet region with λ max =372 nm, and the molar absorptivity of CrO 4 2− in molten (Li/K) 2 CO 3 is calculated. The corrosion rates are investigated by means of increasing the concentration of CrO 4 2− in the melts. Under an air atmosphere, the corrosion rate is slower in molten (Li/K) 2 CO 3 than in molten (Li/Na/K) 2 CO 3 and Cr 2 O 3 corrodes more easily in molten (Li/K) 2 CO 3 than Cr. With an atmosphere of CO 2 =1 atm, there is no increase in the CrO 4 2− concentration in the solution phase during a period of 5 h.

Research Trend of Solid Electrolyte for Lithium Rechargeable Batteries

최근 리튬이차전지는 높은 에너지 밀도와 고용량화되어 급속도로 발전하고 있다. 그 중에서도 친환경 수송 장치의 전기자동차가 주목 받고 있는데 이를 위해서는 리튬이차전지의 많은 성능개선이요구된다. 현재 리튬이차전지는 ‘하이브리드 전기자동차 (Hybrid Electric Vehicle, HEV)’에 실제적용되고 있으며 이를 위해서 높은 용량, 긴 수명, 그리고 안전성 확보가 반드시 필요하다. 하지만현재 리튬이차전지에서 리튬이온의 이동을 위해 사용하는 유기전해액의 과열 및 과충전 상태에서폭발의 위험성을 가지고 있기에 높은 안전성을 가진 고체전해질로의 대체가 시급하다. 따라서 본연구에서는 리튬이차전지의 안정성 및 성능 개선을 위한 고체전해질의 연구 동향과 출원된 특허및 논문에 대하여 논의하고자 한다.Abstract : Recently lithium ion secondary batteries (LIB) have rapidly developed because oftheir advantages such as high energy densities and capacities. Among them, an electrical vehiclewhich is the one of the environmental-friendly transportation facilities has been received a greatattention, but, it is needed to overcome several obstacles of the LIB performances. LIB is practicallyadapted to Hybrid Electric Vehicle (HEV), but the issues for high capacities, long life timeand safety should be solved. Moreover, LIBs still have some possibilities of explosion in the caseof overheating of the used organic electrolyte and overcharging of the cell. Hence, it is urgentlyneeded to replace the liquid electrolytes into the solid electrolytes due to the safety issues.Therefore, in this review, we summarized and discussed the research trends of the solid elec-trolyte to solve the concerns of safety and capacity of LIBs and published patents and articles.Keywords: Solid electrolyte, Li-ion battery, All-solid battery, Safety, LISICON, NASICON

Characterization of (Co/Nb)-coated NiO as a Cathode Material for Molten Carbonate Fuel Cells

C의 용융탄산염과 산소 분위기조건에서 안정하고 높은 전기 전도도를 가지는 장점이 있다. 그러나, 장시간 운전 시 양극에서전해질로의 Ni dissolution은 전지 내부의 단락을 초래하여 전지의 수명을 단축시킨다. 본 연구에서는 대체 전극물질로서 코발트와 나이오븀을 코팅시킨 NiO 전극을 제조하였으며, 이렇게 제조된 전극은 기존 NiO전극과 비교하여 낮은 Ni dissolution과 안정되고 우수한 전기화학 성능을보임을 확인하였다.Abstract: NiO is commonly used as the cathode for the molten carbonate fuel cell due to itsstability and high electrical conductivity in molten carbonates and oxygen atmosphere. However,long-term operation of MCFC has a serious problem which is the degradation of cathode material,the so-called Ni dissolution. In the present study, we have attempted to synthesize a new alter-native cathode material as Co/Nb-coated NiO cathode. The results obtained in this study suggestthat the Co/Nb-coated NiO cathode can be utilized as having lower dissolution and higher cellperformance than those of the pure NiO cathode.Keyword: MCFC, Cathode, Ni dissolution