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@PHDTHESIS{Berger:810808,
      author       = {Berger, Cornelius M.},
      title        = {{S}auerstoffspeicher für die oxidkeramische {B}atterie:
                      {H}erstellung, {C}harakterisierung und {B}etriebsverhalten},
      volume       = {326},
      school       = {Universität Bochum},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-03391},
      isbn         = {978-3-95806-154-5},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {XV, 130 S.},
      year         = {2016},
      note         = {Universität Bochum, Diss., 2016},
      abstract     = {A Rechargeable Oxide Battery (ROB) comprises high
                      temperature regenerative solid oxide cells (rSOC) as energy
                      converters and a porous metal/metal-oxide as storage
                      material for oxygen ions. The rSOCs work in turns in fuel
                      cell- and electrolyzer mode at approximately 800°C. Instead
                      of externally storing the fuel, a stagnant atmosphere
                      consisting of hydrogen and steam is used directly as an
                      oxidizing and reducing agent for the iron base storage
                      material which is located inside the rSOC stack close to the
                      fuel electrode. As a consequence, all the expenses related
                      to pumping losses, heat losses and further components can be
                      avoided, compared to the conventional rSOC system with
                      external storage. Using iron as economic, ecologic, and only
                      feasible storage material results in a maximal theoretical
                      storage capacity of up to 1600 Wh/kg storage. However, the
                      capacity of the battery fades with an increasing number of
                      charge-discharge cycles. Therefore, the scientific
                      challenges in this work are to understand and prevent
                      degradation of the storage medium which is near net-shaped
                      via powder technology. Degradation mainly mainfests as
                      particle coarsening (sintering) and layer formation on top
                      of the porous storage medium. These phenomena entail a
                      decreased active surface and a deteriorated exchange
                      velocity of gas. This work focuses on the effect of the
                      chemical composition and the microstructure on the
                      degradation of the storage components. To mitigate
                      degradation, iron is mixed with stabilising oxides such as
                      calcia (CaO) or zirconia (ZrO$_{2}$). Also, different
                      manufacturing routes and resulting microstructures are
                      evaluated as to whether the degradation properties improve.
                      For accelerated degradation testing, storage components are
                      ex-situ exposed in an environmental furnace to conditions
                      that simulate those present in the battery. Likewise, the
                      electrochemical performance and the long-term stability of
                      the rSOCs are characterized in-situ in battery tests. More
                      than 200 cycles were achieved during battery testing with
                      power densities of 130-170 mW/cm$^{2}$ and durations of more
                      than 60 min/cycle. Microstructural analysis showed that
                      addition of the oxides to the iron base results in a
                      mitigation of degradation effects. Thermogravimetric
                      studies, scanning electron microscopy and Mössbauer
                      spectrometry show a very different mechanism if CaO is used
                      as a scaffold instead of ZrO$_{2}$. While the latter is
                      inert towards iron under battery conditions and acts as a
                      mere spacer between the iron particles, calcia reacts with
                      iron forming a number of mixed oxides depending on the exact
                      partial pressure of oxygen. The reversible formation of
                      mixed oxid phases between iron oxide and calcia leads to a
                      more sustained scaffolding function as compared to when
                      inert ZrO$_{2}$ is used.},
      cin          = {IEK-1},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {135 - Fuel Cells (POF3-135) / SOFC - Solid Oxide Fuel Cell
                      (SOFC-20140602) / HITEC - Helmholtz Interdisciplinary
                      Doctoral Training in Energy and Climate Research (HITEC)
                      (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-135 / G:(DE-Juel1)SOFC-20140602 /
                      G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/810808},
}