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Energy Transformation/Storage

Prof. Dr. Rolf Hempelmann, Dr. Sangwon Kim
We are conducting ‘Electrochemical Energy Transformation and Energy Storage’ project. In this project, we are focusing on two devices: PEM Fuel Cell and Redox Flow Battery. Both are based on Polymer Electrolyte Membrane (PEM) technology. Our project is composed of three subprojects as below.

PEM Fuel Cell

The high-temperature PEM fuel cell (HT-PEM-FC), based on polybenzimidazole membrane doped with phosphoric acid, has a typical operating temperature of 160 °C. The presence of phosphoric acid and dihydrogen phosphate anions, however, considerably slows down the platinum-catalyzed oxygen reduction kinetics at the cathode. Several experimental studies indicate that phosphoric acid and dihydrogen phosphate, respectively, block the electrochemical active centers on the platinum surface.

Proton-conducting ionic liquids (PIL) immobilized in membranes represent alternative electrolytes. Some of PILs exhibit a negligible vapour pressure at temperatures up to 200 °C and a good stability versus hydrolysis, two preconditions for the use in HT-PEM-FCs. The PILs are impregnated in membranes such as sulfonated polyimides or PBI or inert porous separator foil.

Vanadium Redox Flow Battery

The all vanadium redox flow battery (VRFB) has received significant attention because of its excellent electrochemical reversibility, high roundtrip efficiency, and negligible cross-contamination between positive and negative electrolytes. Systems up to multi-MWs have been demonstrated for grid applications and renewable energy integration. The VRFB technology has several advantages over the conventional Li ion or lead acid batteries.

Ionic Liquid Redox Flow Battery

Ionic liquids are fluids/solvents that can participate in a variety of applications such as materials science, electrochemistry and engineering due to their unique physiochemical properties. Recently, ionic liquids have been tentatively tested as solvents for redox flow batteries, due to their thermal and electrochemical stabilities, low vapor pressures and wide potential windows. New ionic liquid-based electrolytes and active redox couples need to be developed.

We collaborate actively with research institutes and companies in Korea and Europe. The representative research partner are listed below.

  • • Saarland University, Transfer Center Sustainable Electrochemistry (TSE) (http://www.sus-e-chem.de)
  • • KIST, Fuel Cell Research Center (http://eng.kist.re.kr/kist_eng/?sub_num=591)
  • • KRICT, Center Membrane (http://english.krict.re.kr/eng/RD02_01 )
  • • FITT, PrimORC ZIM network (http://primorc.de/)
  • • NEXT Energy, Division Fuel Cells (https://www.next-energy.de/en/research-areas/fuel-cells/ )
  • • CNL (http://www.cnl.co.kr/cnl )


Identifying the redox activity of cation-disordered Li-Fe-V-Ti oxide cathdes for Li-ion batteries R. Chen*, R. Witte, R. Heinzmann, S. Ren, S. Mangold, H. Hahn, R. Hempelmann, H. Ehrenberg, S. Indris* Physical Chemistry Chemical Physics, 2016,18, 7695-7701 DOI: 10.1039/C6Cp00131A
HIgh-performance low temperature Li+intercalation in disordered rock-salt Li-Cr-V oxyfluorides R. Chen*, S. Ren, X. Mu, E. Maawad, S. Zander, R. Hempelmann, H.Hahn ChemElectroChem 2016.3,892-895. DOI: 10.1002/celc.201600033R1
Lithiation-driven structural transition of VO2F into disordered rock-salt LixVo2f R. Chen*, E. Maawad, M. Knapp, S. Ren, P.Beran, R. Witter, R. Hempelmann RSC Adv. 2016,6,65112-65118
Ionic liquid-mediated aqueous redox flow batteries for high voltage applications R. Chen*, R. Hempelmann Electrochemistry Communications, 2016, 70, 56-59
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