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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},
}