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@PHDTHESIS{Loutati:1043158,
      author       = {Loutati, Asmaa},
      title        = {{O}ptimization of {N}a{SICON}-type lithium- ion conductors
                      for solid-state batteries},
      volume       = {664},
      school       = {Duisburg-Essen},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-02774},
      isbn         = {978-3-95806-824-7},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {viii, 104},
      year         = {2025},
      note         = {Dissertation, Duisburg-Essen, 2024},
      abstract     = {The continuing depletion of fossil fuels, rising oil prices
                      and the need to reduce CO2 emissions have stimulated
                      intensive research into alternative energy technologies
                      based on renewable and clean sources. Among the various
                      technologies, electrochemical energy storage in rechargeable
                      lithium-ion batteries (LIBs) plays an important role, both
                      for powering a wide range of electronic devices and electric
                      vehicles, and for storing electricity generated from
                      alternative energy sources such as solar and wind.
                      Commercial LIBs using organic liquid electrolytes dominate
                      the market. However, the reactivity of liquid electrolytes
                      at very positive or negative potentials limits the choice of
                      suitable electrode materials and thus the available energy
                      density. In addition, the toxicity and flammability of
                      organic electrolytes raise serious safety concerns. As an
                      alternative to conventional liquid electrolyte LIBs,
                      solid-state battery (SSB) concepts using solid electrolytes
                      (SEs) are currently under intense investigation. Among
                      numerous classes of materials, ceramic SEs are particularly
                      attractive due to their non-flammability, relatively high
                      ionic conductivity at room temperature (RT) and high
                      chemical stability in air, resulting in potentially very
                      high intrinsic safety of the batteries. In particular,
                      Li-containing NaSICONs (Na Super Ionic CONductors) are
                      currently receiving a great deal of attention due to the
                      large structural variability and high ionic conductivity
                      that can be achieved by substituting the lattice framework
                      with various elements. Within this class of materials,
                      lithium aluminum germanium phosphate Li1+xAlxGe2-x(PO4)3
                      (LAGP) and lithium aluminum titanium phosphate
                      Li1+xAlxTi2-x(PO4)3 (LATP) are solid-state Li-ion conductors
                      with the highest ionic conductivity at RT. However, the main
                      drawback of germanium and titanium-containing materials is
                      the low electrochemical stability at negative potentials
                      caused by the reduction of Ge4+ to Ge2+ and Ti4+ to Ti3+,
                      which prevents the use of lithium metal anodes and reduces
                      the energy density of the battery. To overcome this problem,
                      the aim of this work was to increase the reduction stability
                      of NaSICON compounds by replacing Ge and Ti with more
                      reduction stable ions. To this end, various compositions of
                      the type Li1+xM3+xZr2-x(PO4)3, where M3+ = Al3+, Sc3+, Y3+,
                      were synthesized by solution-assisted solid-state reaction.
                      The effect of Substitution on crystallographic parameters,
                      relative density, sintering temperature, ionic conductivity,
                      and electrochemical stability was systematically
                      investigated. The cationic substitution of M3+ (M = Al, Sc,
                      Y) for Zr4+ in LiZr2(PO4)3 (LZP) stabilizes the rhombohedral
                      NaSICON structure (space group 𝑅3̅ c) at RT and
                      increases the ionic conductivity significantly. Here, at 25
                      °C and with a comparable relative density of 94-96 $\%,$ an
                      ionic conductivity of 2.7 × 10-5 S cm-1, 6.7 × 10-5 S cm-1
                      and 3.6 × 10-6 S cm-1 was achieved with the compositions
                      Li1.2Sc0.2Zr1.8(PO4)3, Li1.2Y0.2Zr1.8(PO4)3 and
                      Li1.2Al0.2Zr1.8(PO4)3, respectively. Compared to
                      Li1+xScxZr2-x(PO4)3, the Y3+ substitution in LZP slightly
                      enhanced the ionic conductivity and marked the maximum
                      Li+-ion conductivity at RT with composition x = 0.2 in the
                      whole system Li1+xM3+xZr2-x(PO4)3. However, the
                      Al3+-substitution decreased the ionic conductivity at RT. In
                      addition to cationic substitution, the effect of polyanionic
                      substitution on ionic conductivity was investigated in the
                      two materials series Li3+xSc2SixP3-xO12 (0 ≤ x ≤ 0.6)
                      and Li1.2+xSc0.2Zr1.8SixP3-xO12 (0.3 ≤ x ≤ 2.8). The
                      substitution of (PO4)3- with (SiO4)4- in the system
                      Li2O-Sc2O3-ZrO2-SiO2-P2O5 effectively lowers the sintering
                      temperature. Moreover, the introduction of zirconium can
                      limit the evaporation of lithium species even at high
                      sintering temperature. Silicate substitution in
                      Li3+xSc2SixP3-xO12 (0 ≤ x ≤ 0.6) has been shown to
                      stabilize the monoclinic Symmetry (space group P21/n)
                      resulting in the increase of total ionic conductivity. The
                      ionic conductivity at 25 °C increased from 2 × 10-6 S cm-1
                      for x = 0 to 1.2 × 10-5 S cm-1 for x = 0.15, which is the
                      highest ionic Conductivity of the investigated compositions
                      in the Li2O-Sc2O3-ZrO2-SiO2-P2O5 system. The purity of the
                      NaSICON materials has a strong influence on the grain
                      boundary resistance and thus on the ionic conductivity.
                      Selected ceramic NaSICON electrolytes such as LZP ,
                      Li1.2Y0.2Zr1.8(PO4)3, and Li3Sc2(PO4)3 (LSP) were found to
                      be more stable with respect to lithium than LATP and LAGP.
                      LSP proved to be chemically and electrochemically very
                      stable and might act as an anode protection material in
                      combination with lithium metal.},
      cin          = {IMD-2},
      cid          = {I:(DE-Juel1)IMD-2-20101013},
      pnm          = {1222 - Components and Cells (POF4-122)},
      pid          = {G:(DE-HGF)POF4-1222},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2506230903296.203072864795},
      doi          = {10.34734/FZJ-2025-02774},
      url          = {https://juser.fz-juelich.de/record/1043158},
}