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@INPROCEEDINGS{Neuhaus:1044596,
      author       = {Neuhaus, Kerstin and Machitouen, Meriem and Mowe, Patrick
                      and Krämer, Susanna and Windmüller, Anna and Jüstel,
                      Thomas and Winter, Martin},
      title        = {{A}nalysis of the {F}ranklinite-{G}ahnite
                      ({Z}n{F}e2-x{A}lx{O}4) {S}olid {S}olution {S}eries:
                      {I}nsights into the {U}se of {D}oped {F}errites as {A}ctive
                      {M}aterial for {Z}inc-ion {B}atteries},
      reportid     = {FZJ-2025-03269},
      year         = {2025},
      abstract     = {The cubic spinel franklinite (zinc ferrite, ZnFe2O4) is a
                      well-studied material with a comparatively small band gap of
                      1.9 eV and widely studied magnetic properties [1,2]. This
                      makes it a compelling candidate for a number of different
                      applications ranging from photocatalysis to data storage.
                      Recently, there have also been attempts to use zinc ferrite
                      as an active material at the negative electrode of
                      lithium-ion batteries (LIBs) due to its high theoretical
                      volumetric capacity of 1142 mA h cm-3, but these have failed
                      due to the poor chemical stability of the material during
                      repeated lithium (de)insertion [1-3]. In contrast, first
                      attempts to use doped zinc ferrite as an active material at
                      the positive electrode of zinc-ion batteries (ZIB) showed
                      promising results [4]. Compared to the standard tetragonal
                      spinel material ZnMn2O4, the cubic titanium-doped ferrite in
                      this study showed higher potentials vs. Zn/Zn2+. However,
                      the problems of transition metal leaching in contact with
                      aqueous electrolytes were similar to those of manganite.In
                      the present study on the solid solution series of
                      franklinite-gahnite, the iron is partially or completely
                      replaced by Al3+. Since iron leaching occurs especially when
                      Fe3+ in the structure is reduced to Fe2+ upon Zn2+
                      insertion, a sufficient amount of non-redox-active Al3+
                      could stabilize the structure in contact with aqueous
                      electrolytes, but will strongly affect the ionic
                      conductivity and possibly the cyclability. According to LIB
                      studies, there might be a sweet spot in the range below x =
                      1.0 for ZnFe2-xAlxO4 [5]. In addition, increasing the
                      aluminum content will result in lower electron conductivity
                      due to an increased band gap [6], which is not necessarily
                      desirable for an active material, but can be compensated by
                      techniques such as carbon coating. It is also expected that
                      the magnetic and optical properties will change
                      significantly with increasing Al content. Homogeneous
                      powders with the composition ZnFe2-xAlxO4 (x = 0.0 to 2.0)
                      were synthesized by a Pechini type synthesis method.
                      Calcined powders were then used to produce electrode sheets
                      for application in ZnFe2-xAlxO4 ||Zn cells, while sintered
                      ceramic pellets were used for materials level
                      investigations. Using a variety of analytical techniques
                      (XRD, impedance spectroscopy, CV, reflectance measurements,
                      etc.) we succeeded in obtaining a holistic picture of the
                      entire solid solution series, which will be discussed in
                      terms of a defect model and potential applications in ZIB
                      and beyond.REFERENCES[1] W. Schiessl, W. Potzel, H. Karzel,
                      M. Steiner, G.M. Kalvius, Phys. Rev. B 53 (1996) 9143[2] M.
                      Bohra, V. Alman, R. Arras, Nanomater 1 (2021) (5) 1286[3]
                      M.M. Thackeray, Adv Energy Mater 11 (2021) (2) 2001117[4] S.
                      Krämer, J. Hopster, A. Windmüller, M. Grünebaum, R.-A.
                      Eichel, T. Jüstel, M. Winter, K. Neuhaus, Energy Adv. 3
                      (2024) 2175[5] I. Quinzeni, V. Berbenni, D. Capsoni, M.
                      Bini, J. Solid State Electrochem. 22 (2018) 2013-2024[6] S.
                      Gul, M.A. Yousuf, A. Anwar, M.F. Warsi, P.O. Agboola, I.
                      Shakir, M. Shahid, Ceram. Internat. 46 (2020) 14195-14205},
      month         = {May},
      date          = {2025-05-06},
      organization  = {Battery 2030+, Münster (Germany), 6
                       May 2025 - 7 May 2025},
      subtyp        = {After Call},
      cin          = {IMD-4},
      cid          = {I:(DE-Juel1)IMD-4-20141217},
      pnm          = {1221 - Fundamentals and Materials (POF4-122)},
      pid          = {G:(DE-HGF)POF4-1221},
      typ          = {PUB:(DE-HGF)24},
      doi          = {10.34734/FZJ-2025-03269},
      url          = {https://juser.fz-juelich.de/record/1044596},
}