Sung-Hee Roh

Novel core–shell structure of a lead-activated carbon (Pb@AC) for advanced lead–acid battery systems

To enhance the power and energy densities of advanced lead–acid batteries (Ad-LAB), a novel core–shell structure of lead-activated carbon (Pb@AC) was prepared and used as a negative electrode active material. The AC could be formed as a shell around a core of Pb nanoparticles. The active core–shell structures were synthesized using a simple chemical process to overcome the limitations in the negative Pb electrode, specifically the large crystallization of lead sulfate (PbSO4) that leads to a short cycle life. The key role of the carbon material in the negative electrode is to enhance the electrochemical performances and decrease the formation of PbSO4. The X-ray diffraction study reveals that the formation of lead oxide was prevented by the AC during the synthetic process. The novel core–shell structure of Pb@AC was confirmed through transmission electron microscopy. In order to obtain high-performance Ad-LAB, a high surface area of the AC is necessary to provide a super capacitive effect in the negative electrode. The unit cell performance of the as-prepared active materials exhibits significant increased discharge capacity at 1C rate. The unit cell with the Pb@AC negative electrode has a capacity per unit volume of 0.0165 Ah/cc. Hence, the low cost of AC and the simple synthetic core–shell structure of Pb@AC make this material a promising negative electrode active material for Ad-LAB applications.

The Effect of sGO Content in sPEEK/sGO Composite Membrane for Unitized Regenerative Fuel Cell

Abstract Polymer electrolyte membrane for unitized regenerative fuel cells requires high proton conductivity, high dimensional stability, low permeability, and low cost. However, DuPo nt’s Nafion which is a commercial polymer electrolyte membrane has high permeabili ty, high cost, and decreasing proton conductivity and dimensional stability over 80°C. To address these problems, sulfonated poly ether ether ketone (sPEEK) which is a low cost hydrocarbon polymer is selected as matrix polymer for the preparation of polymer elect rolyte membrane. In addition, composite membrane with improved proton conductivity and dimensional stability is prepared by introducing sulfonated graphene oxide (sGO). The fundamental properties of polymer electrolyte membranes are analyzed by investigating membrane’s water content, dimensional stability, proton conductivity, and morphology. The cell test is conducted to consider the possibility of application of sPEEK/sGO composite membrane for an unitized regenerative fuel cell.