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@PHDTHESIS{Kiyek:1038890,
      author       = {Kiyek, Vivien},
      title        = {{O}xide-based {A}ll-{S}olid-{S}tate {B}atteries for and
                      from {R}ecycling {P}rocesses},
      volume       = {656},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-01701},
      isbn         = {978-3-95806-806-3},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {viii, 128, xix},
      year         = {2025},
      note         = {Dissertation, RWTH Aachen University, 2024},
      abstract     = {All-Solid-State Batteries (ASSB) are considered to be one
                      of the most promising future battery technologies due to the
                      prospect of increased safety and energy density. ASSB can be
                      categorized into three main classes: Polymers, Sulfides and
                      Oxides, which are the focus of this work. Ceramic oxides,
                      among others, are suitable to replace current liquid
                      electrolytes of Lithium-ion batteries (LIBs), with the
                      advantage of being the only solid electrolyte (Li7La3Zr2O12,
                      LLZO) that is stable to Li metal. Li metal as an anode
                      material provides a higher energy density in the battery and
                      can overcome the foreseeable limits of liquid electrolytes.
                      In addition, ceramic oxide solid electrolytes increase
                      safety due to the high thermal stability of ceramic
                      materials. Disadvantages of LLZO are the high processing
                      cost and energy requirements, leading to high embodied
                      energy due to the multiple long calcination times at high
                      temperatures. Also, LLZO production requires raw materials
                      beyond Li, Co, Ni and Mn, which are wellknown from the
                      cathode materials in LIBs. Notably, Ta, and Ga are listed as
                      critical raw materials. This is one of the main reasons why
                      recycling is important for both current LIBs and future ASSB
                      batteries. The current EU directive requires a recycling
                      rate of $70\%$ of complete batteries in 2030, while
                      individual materials such as Co, Ni, should have recycling
                      rates of up to $90\%.$ In the present work, a cost- and
                      energy-efficient direct recycling route for LLZO components
                      is developed via re-lithiation of LLZO waste materials by
                      adding a Li source during heat treatment. Abnormal grain
                      growth as a possible result of sintering LLZO tapes under Li
                      excess is analyzed, and the responsible mechanism is
                      investigated and explained. It is demonstrated successfully
                      that sintering with Li2CO3 is able to re-lithiate degraded
                      LLZO: Similar behavior to freshly synthesized LLZO separator
                      material is observed, while the critical current density
                      (CCD) is even increased to 0.75 mA cm−2, exceeding the
                      recently reported values for tapes made from freshly
                      synthesized LLZO powder in a comparable process. This
                      re-lithiation route therefore represents the first
                      successful approach to a direct recycling of LLZO
                      components, able to save time and cost as well as to
                      preserve the embodied energy in the LLZO. The second part of
                      the thesis addresses the high process cost and energy
                      consumption of LLZO synthesis. Here, a new process route is
                      developed, where tape casting of precursors powder of LLZO
                      leads to the formation of LLZO in-situ during the sintering
                      step. The application of this process onto both the
                      separator and the composite cathode, a special designed
                      cathode for example for oxide-solidstate batteries, is then
                      evaluated. The composite cathode with LCO-LLZO shows highly
                      promising behavior as the Co-ion diffusion, a disadvantage
                      of co-sintering of already pre-synthesized LLZO powder
                      mixtures, that is very hard to avoid, is suppressed in this
                      new process. Although Al-ion diffusion still occurs, the
                      general properties of the composite cathodes, such as
                      density and flatness are very promising. For the LLZO
                      separator, Ta doping and Ga doping with the new process
                      route were investigated. Both result in a low-density tape,
                      however, density can be tuned by adding pre-synthesized LLZO
                      particles to the slurry. These findings can hence be used as
                      well to create a porous-dense-porous LLZO layer with the new
                      process, as the porous LLZO framework represents an
                      interesting approach for zero-strain electrode layers.
                      Finally, a recycled precursor material is used in the new
                      process, which shows first good results for an LLZO
                      separator tape. This suggests that the new process is
                      applicable also for recycled raw material, although further
                      process fine-tuning is required. As a result, the overall
                      process time is reduced by $65\%,$ while individual steps
                      are reduced by more than $98\%.$ This translates into a
                      reduction of the overall throughput time from 40 hours oven
                      time at the highest temperature (with sintering 45 hours
                      (LLZO) or 42 hours (LCO-LLZO)) to only 5 hours (LLZO) or 2
                      hours (LCO-LLZO) at the highest temperature, a significant
                      advantage for industrial upscaling. Also, energy input is
                      considerably reduced as the majority of the energy-intensive
                      heat treatment steps are saved $(80\%).$ This reduction in
                      time and energy demand ultimately reduces the production
                      cost of LLZO.},
      cin          = {IMD-2},
      cid          = {I:(DE-Juel1)IMD-2-20101013},
      pnm          = {1221 - Fundamentals and Materials (POF4-122)},
      pid          = {G:(DE-HGF)POF4-1221},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      doi          = {10.34734/FZJ-2025-01701},
      url          = {https://juser.fz-juelich.de/record/1038890},
}