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@PHDTHESIS{Guin:830267,
      author       = {Guin, Marie},
      title        = {{C}hemical and physical properties of sodiumionic
                      conductors for solid-state batteries},
      volume       = {373},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-03840},
      isbn         = {978-3-95806-229-0},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {ix, 126 S.},
      year         = {2017},
      note         = {RWTH Aachen, Diss., 2017},
      abstract     = {The electrochemical storage of electricity in batteries is
                      one key solution to the future extensive use of renewable
                      energy sources. Lithium ion batteries have received intense
                      attention since they provide the largest energy density and
                      output voltage. They have yet to be optimized in terms of
                      capacity, safety and cost and the search for alternatives to
                      lithium has already gained popularity in the past years
                      because of the shortage of resources. One popular substitute
                      is sodium since its chemical properties are similar to those
                      of lithium and sodium is an abundant element. Sodium
                      technologies are not new but the commercial sodium-ion
                      batteries operate at temperatures as high as 300 °C raising
                      safety issues and discussion about the energy needed to heat
                      the battery. Therefore, solid-state sodium batteries
                      operating at room temperature present a safer alternative as
                      they are leak proof and non-flammable. In addition, no
                      supplementary heating equipment is needed to operate the
                      battery. The key in designing safe and efficient solid-state
                      Na-ion batteries is the development of highly conductive
                      solid electrolytes that also display high thermal and
                      chemical stability. Amongst all possibilities, one class of
                      ceramic electrolytes is of great interest: the so-called
                      NASICON materials with general formula AM(PO$_{4)3}$ (in
                      this work, A = Na). They display very attractive
                      compositional diversity and are likely to achieve high
                      conductivity. In this thesis, an extensive study of the
                      composition, the crystal structure and the conductivity of
                      approximately 110 Na-conducting NASICON materials was
                      conducted to find guidelines for designing highly conductive
                      NASICON type materials. For NASICON with aliovalent
                      substitution, the electroneutrality is guaranteed by
                      adapting the amount of Na per formula unit and an optimal Na
                      concentration of 3.2-3.5 mol was identified. Furthermore, an
                      optimal size for the M cations in the structure was
                      highlighted. In addition, the substitution of P with Si
                      proved to have a positive impact on the conductivity. Using
                      these guidelines, the solid solution
                      Na$_{3+x}$Sc$_{2}$(SiO$_{4)x}$(PO$_{4)3-x}$ was investigated
                      for the first time. Various compositions with 0 $\le$ x
                      $\le$ 0.8 were prepared by solid state reaction and their
                      crystallographic and electrical properties were
                      investigated. As a result, the high conductivity at room
                      temperature of 8.3 x 10$^{-4}$ S cm$^{-1}$ was obtained for
                      x = 0.4. In addition, the criteria for high conductivity
                      concluded from the literature study were verified and
                      completed with data of bulk conductivity for the solid
                      solution. This systematic study of the substitution of P
                      with Si provided better insights in the conduction pathway
                      of the sodium ions in the NASICON structure. Finally, thick,
                      dense pellets of
                      Na$_{3.4}$Sc$_{2}$Si$_{0.4}$P$_{2.6}$O$_{12}$ were used as
                      solid electrolyte in different solid-state battery designs
                      and for the first time, a solid-state Na battery based on
                      inorganic materials was cycled at room temperature.},
      cin          = {IEK-1},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {131 - Electrochemical Storage (POF3-131)},
      pid          = {G:(DE-HGF)POF3-131},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/830267},
}