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@INPROCEEDINGS{Schierholz:1019737,
      author       = {Schierholz, Roland and Dzieciol, Krzysztof and Tempel,
                      Hermann and Kungl, Hans and Eichel, Rüdiger-A. and Zhang,
                      Qian},
      title        = {3{D}-microstructure of spindle-like {L}i1{T}i2({PO}4)3
                      particles revealed by electron microscopy},
      reportid     = {FZJ-2023-05568},
      year         = {2023},
      abstract     = {1. Introduction Pure Li1Ti2(PO4)3 (LTP) is an anode
                      material with NASICON structure and a lithiation potential
                      of 2.31 V.[1] This potential fits the electrochemical
                      stability window of the promising isostructural solid state
                      electrolyte Li1+xAlxTi2-x(PO4)3 (LATP, which is obtained by
                      trivalent substitution and application in an all-phosphate
                      solid state battery has been demonstrated.[2] Comparison of
                      different synthesis methods revealed an enhanced cycling
                      performance of solvothermally prepared LTP with spindle-like
                      particles of 2 – 5 µm size compared to the same material
                      prepared by sol-gel based Pecchini method.[3] 2.
                      ObjectivesScanning electron microscopy (SEM) suggests that
                      spindle-like particles are formed by sub particles of about
                      300 nm size, but as only the surface is accessible by SEM
                      the origin of the enhanced performance remains unclear. With
                      focused ion beam (FIB) and (Scanning) Transmission Electron
                      Microscopy the inner volume can be characterized to give a
                      complete picture of the particles crystal and microstructure
                      as well as its local chemical composition. 3. Materials and
                      methodsThe particles were synthesized by solvothermal
                      reaction, consecutively vacuum dried and annealed at 800
                      °C.[3] These particles were then dispersed in ethanol and a
                      droplet was put on a silicon wafer for FIB-SEM experiments.
                      FIB tomography and TEM-lamella preparation were conducted
                      with a Helios Nanolab 460F1, FEI, Netherlands.[4] TEM and
                      STEM analysis was conducted in a Tecnai F20 and a Titan G2
                      Crewley.[5]4. ResultsSEM imaging shows the morphology, with
                      sub particles forming a dumbbell like particle, and already
                      provides hints for the presence of two secondary phases, on
                      nanoparticles, the other a bulky phase with different
                      surface morphology. The presence oof different phases is
                      approved by chemical contrast in BSE-images of cross
                      sections and STEM HAADF imaging. STEM-EDS gives an estimate
                      of the chemical compositions which is completed by STEM-EELS
                      for the detection of Lithium. HRTEM and HRSTEM could then
                      identify the crystallographic structures of these secondary
                      phases to be TiO2 anatase for the nanoparticles and LiTiPO5
                      (Pnma ICSD #153522) for the bulky secondary phase.
                      FIB-tomography revealed that the majority of the TiO2
                      nanoparticles are interconnected.5. ConclusionsThe complex
                      microstructure of the spindle-like LTP particles can only be
                      solved by a combination of FIB-tomography and STEM-analysis.
                      The three-dimensional network of TiO2-nanoparticles seem to
                      improve the cycling behavior, as it may enhance the
                      diffusion and can also contribute to capacity and is no dead
                      material.[6] [1] S. Yu et al., ACS Appl. Mater. Interfaces
                      (2018) Vol. 10, No. 26 p. 22264-22277
                      https://doi.org/10.1021/acsami.8b05902 [2] H. Aono et al.,
                      Journal of The Electrochemical Society , (1990) 137, 4, p.
                      1023-1027 https://doi.org/10.1149/1.2086597 [3] S. Yu et
                      al., ChemElectroChem (2016) Vol. 3, No. 7, p. 1157-1169
                      https://doi.org/10.1002/celc.201600125 [4] M. Kruth et al.,
                      Journal of large-scale research facilities JLSRF (2016) 2,
                      A59 https://doi.org/10.17815/jlsrf-2-105 [5] A. Kovács et
                      al., Journal of large-scale research facilities JLSRF (2016)
                      2, A43 https://doi.org/10.17815/jlsrf-2-68 [6] M. Madian et
                      al., Batteries (2018) 4, 7,
                      https://doi.org/10.3390/batteries4010007 [7] M.L. Sushko
                      Mechanism of Li+/Electron Conductivity in Rutile and Anatase
                      TiO2 Nanoparticles J. Phys. Chem. C , (2012) 114, 47
                      American Chemical Society, p. 20277-20283
                      https://doi.org/10.1021/jp107982c Figure 1: SEM-BSE image of
                      a typical spindle-like LTP-particle.},
      month         = {Feb},
      date          = {2023-02-26},
      organization  = {Microscopy Conference, Darmstadt
                       (Germany), 26 Feb 2023 - 2 Mar 2023},
      subtyp        = {Other},
      cin          = {IEK-9},
      cid          = {I:(DE-Juel1)IEK-9-20110218},
      pnm          = {1121 - Digitalization and Systems Technology for
                      Flexibility Solutions (POF4-112)},
      pid          = {G:(DE-HGF)POF4-1121},
      typ          = {PUB:(DE-HGF)24},
      url          = {https://juser.fz-juelich.de/record/1019737},
}