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@INPROCEEDINGS{Gross:1019927,
      author       = {Gross, Jürgen and Dashjav, Enkhtsetseg and Tietz, Frank
                      and Malzbender, Jürgen and Ziegner, Mirko and Grüner,
                      Daniel and Peter, Nicolas and Schwaiger, Ruth},
      title        = {{M}icrostructural properties of tape-cast {LATP} ceramic
                      sheets for application in solid state batteries},
      reportid     = {FZJ-2023-05748},
      year         = {2023},
      abstract     = {Solid-state batteries (SSB) are promising candidates for
                      the next generation of energy storage devices, since this
                      technology promises vastly improved safety and storage
                      capacity compared to conventional Li-ion batteries [1]. In
                      order to enable this technology further improvements of the
                      solid electrolyte (SE) in regards to manufacturing, ionic
                      conductivity, microstructural and mechanical properties have
                      to be made [2-4]. The solid electrolyte Li1+xAlxTi2-x(PO4)3
                      (LATP) is a promising material for the application as SE, in
                      particular due to its high ionic conductivity and good
                      compatibility towards certain active materials such as
                      LiFePO4 [5-7]. Furthermore, in contrast to hygroscopic SEs,
                      such as Li7La3Zr2O12, LATP exhibits a high stability against
                      H2O and CO2 [8, 9], thus enabling production and handling in
                      ambient air, leading to reduced production costs. Advanced
                      components require industrial relevant production processes,
                      of which in particular tape casting is of considerable
                      interest. Processing-relevant sintering behavior needs to be
                      optimized using sintering additives. Thus, 14 variations of
                      tape-cast LATP with different chemical compositions and
                      varying amounts of LiF and SiO2 additions have been
                      investigated with respect to their microstructure and
                      especially their phase compositions. A comparison of their
                      chemical and phase composition revealed an increase in the
                      amount of the orthorhombic LATP phase with increasing
                      lithium content, indicating that orthorhombic LATP is a
                      lithium-rich modification. The orthorhombic LATP phase
                      exhibit a much lower ionic conductivity compared to its
                      rhombohedral modification, thus has a negative effect on the
                      battery performance. Based on high-temperature X-ray
                      diffraction, a rhombohedral – orthorhombic LATP phase
                      equilibrium was identified, shifting towards the
                      rhombohedral phase at temperatures > 800 °C. Above 1000 °C
                      no orthorhombic LATP could be detected, therefore an
                      additional heat treatment dissolves this phase, potentially
                      improving the materials property, however it is known at
                      higher sintering temperatures the severity of microcracks
                      within LATP increases. SEM micrograph analysis revealed that
                      both LiF and SiO2 are beneficial for the densification of
                      the material. Although increased SiO2 addition led to
                      decreased densifications, the SiO2 addition successfully
                      inhibited the LATP grain growth, leading to smaller average
                      grain sizes, thus reducing the severity of micro-cracks.
                      Based on Ball-on-3 balls bending results an increase of the
                      material strength with decreasing porosity can be observed,
                      however below $18\%$ porosity, a sharp drop of the material
                      strength from ~150 MPa to ~50 MPa is detected. Fracture
                      surface analysis revealed a shift of the fracture origin,
                      where at higher porosities $(>18\%)$ pores and at lower
                      porosities $(<18\%)$ micro-cracks are causing material
                      failure under applied stress. This might be expected since
                      dense tape cast LATP requires higher sintering temperatures,
                      although the use of SiO2 as a sintering additive appears to
                      be a promising approach to reduce the micro-crack severity.
                      However based on these result the application of dense LATP
                      in solid state batteries is not straight forward. Porous
                      tape cast LATP on the other hand, might be used as a
                      skeleton-structure for polymer infiltrated cathode
                      composites, since it can be obtained at lower sintering
                      temperatures. However, a high amount of o-LATP might be
                      expected, which requires clarification of its effects also
                      on the performance of cathode composites, which will be the
                      aim of future studies.[1] F. Zheng, M. Kotobuki, S. Song, M.
                      O. Lai, and L. Lu, "Review on solid electrolytes for
                      all-solid-state lithium-ion batteries," Journal of Power
                      Sources, vol. 389, pp. 198-213, 2018.[2] R. Chen, W. Qu, X.
                      Guo, L. Li, and F. Wu, "The pursuit of solid-state
                      electrolytes for lithium batteries: from comprehensive
                      insight to emerging horizons," Materials Horizons, vol. 3,
                      no. 6, pp. 487-516, 2016.[3] A. Manthiram, X. Yu, and S.
                      Wang, "Lithium battery chemistries enabled by solid-state
                      electrolytes," Nature Reviews Materials, vol. 2, no. 4, pp.
                      1-16, 2017.[4] T. Shi, Y.-Q. Zhang, Q. Tu, Y. Wang, M.
                      Scott, and G. Ceder, "Characterization of mechanical
                      degradation in an all-solid-state battery cathode," Journal
                      of Materials Chemistry A, vol. 8, no. 34, pp. 17399-17404,
                      2020.[5] E. Dashjav et al., "Microstructure, ionic
                      conductivity and mechanical properties of tape-cast Li1.
                      5Al0. 5Ti1. 5P3O12 electrolyte sheets," Journal of the
                      European Ceramic Society, 2020.[6] E. Dashjav et al., "The
                      influence of water on the electrical conductivity of
                      aluminum-substituted lithium titanium phosphates," Solid
                      State Ionics, vol. 321, pp. 83-90, 2018.[7] M. Gellert, E.
                      Dashjav, D. Grüner, Q. Ma, and F. Tietz, "Compatibility
                      study of oxide and olivine cathode materials with lithium
                      aluminum titanium phosphate," Ionics, vol. 24, no. 4, pp.
                      1001-1006, 2018.[8] G. y. Adachi, N. Imanaka, and H. Aono,
                      "Fast Li⊕ conducting ceramic electrolytes," Advanced
                      Materials, vol. 8, no. 2, pp. 127-135, 1996.[9] E.
                      Bucharsky, K. Schell, A. Hintennach, and M. Hoffmann,
                      "Preparation and characterization of sol–gel derived high
                      lithium ion conductive NZP-type ceramics Li1+ x AlxTi2− x
                      (PO4) 3," Solid State Ionics, vol. 274, pp. 77-82, 2015.},
      month         = {Jun},
      date          = {2023-06-12},
      organization  = {Helmholtz Energy Conference 2023,
                       Koblenz (Germany), 12 Jun 2023 - 13 Jun
                       2023},
      subtyp        = {After Call},
      cin          = {IEK-2 / IEK-1},
      cid          = {I:(DE-Juel1)IEK-2-20101013 / I:(DE-Juel1)IEK-1-20101013},
      pnm          = {1221 - Fundamentals and Materials (POF4-122) / ProFeLi -
                      Produktionstechnik für Festkörperbatterien mit
                      Lithium-Metall-Anode (13XP0184B)},
      pid          = {G:(DE-HGF)POF4-1221 / G:(BMBF)13XP0184B},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/1019927},
}