Browsing by Author "Vanita, Vanita"

Filter results by typing the first few letters
Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    Conductivity enhancement within garnet‐rich polymer composite electrolytes via the addition of succinonitrile
    (2022) Vanita, Vanita; Waidha, Aamir Iqbal; Yadav, Sandeep; Schneider, Jörg J.; Clemens, Oliver
    All‐solid‐state lithium‐ion batteries (ASSLIBs) are promising alternatives to conventional organic electrolyte‐based batteries due to their higher safety and higher energy densities. Despite advantages, ASSLIBs suffer from issues like high charge transfer resistances due to the brittleness of the inorganic solid electrolyte and chemical instabilities at the lithium/electrolyte interface. Within this work, we investigate composite electrolytes (CEs) based on garnet‐type Li6.4La3Zr1.4Ta0.6O12 (LLZTO), polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide, prepared via a solvent‐free cryo‐milling approach in contrast to conventional solvent‐mediated synthesis. Compositions ranging from polymer‐rich to garnet‐rich systems are investigated via X‐ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy in order to determine the compatibility of the cryo‐milling process toward membrane fabrication along with the possible chemical interactions between the composite membrane components. Electrochemical impedance spectroscopy is used to study the role of ceramic to polymer weight fraction on ionic conductivity. It is shown that the addition of succinonitrile (SCN) to the garnet‐rich CEs can significantly improve the ionic conductivity compared to the SCN‐free CEs.
  • Thumbnail Image
    ItemOpen Access
    Insights into the first multi-transition-metal containing Ruddlesden-Popper-type cathode for all-solid-state fluoride ion batteries
    (2024) Vanita, Vanita; Waidha, Aamir Iqbal; Vasala, Sami; Puphal, Pascal; Schoch, Roland; Glatzel, Pieter; Bauer, Matthias; Clemens, Oliver
    Promising cathode materials for fluoride-ion batteries (FIBs) are 3d transition metal containing oxides with Ruddlesden-Popper-type structure. So far, the multi-elemental compositions have not been investigated, but it could alternate the electrochemical performance similar to what has been found for cathode materials for lithium-ion batteries. In this study, we investigate RP type La2Ni0.75Co0.25O4.08 as an intercalation-based active cathode material for all-solid-state FIBs. We determine the structural changes of La2Ni0.75Co0.25O4.08 during fluoride intercalation/de-intercalation by ex situ X-ray diffraction, which showed that F- insertion leads to transformation of the parent phase to three different phases. Changes in the Ni and Co oxidation states and coordination environment were examined by X-ray absorption spectroscopy and magnetic measurements in order to understand the complex reaction behaviour of the phases in detail, showing that the two transition metals behave differently in the charging and discharging process. Under optimized operating conditions, a cycle life of 120 cycles at a critical cut-off capacity of 40 mA h g-1 against Pb/PbF2 was obtained, which is one of the highest observed for intercalation electrode materials in FIBs so far. The average coulombic efficiencies ranged from 85% to 90%. Thus, La2Ni0.75Co0.25O4.08 could be a promising candidate for cycling-stable high-energy cathode materials for all-solid-state FIBs.
  • Thumbnail Image
    ItemOpen Access
    On the surface modification of LLZTO with LiF via a gas-phase approach and the characterization of the interfaces of LiF with LLZTO as well as PEO+LiTFSI
    (2022) Donzelli, Manuel; Ferber, Thimo; Vanita, Vanita; Waidha, Aamir Iqbal; Müller, Philipp; Mellin, Maximilian; Hausbrand, René; Jaegermann, Wolfram; Clemens, Oliver
    In this study we present gas-phase fluorination as a method to create a thin LiF layer on Li6.5La3Zr1.5Ta0.5O12 (LLZTO). We compared these fluorinated films with LiF films produced by RF-magnetron sputtering, where we investigated the interface between the LLZTO and the deposited LiF showing no formation of a reaction layer. Furthermore, we investigated the ability of this LiF layer as a protection layer against Li2CO3 formation in ambient air. By this, we show that Li2CO3 formation is absent at the LLZTO surface after 24 h in ambient air, supporting the protective character of the formed LiF films, and hence potentially enhancing the handling of LLZTO in air for battery production. With respect to the use within hybrid electrolytes consisting of LLZTO and a mixture of polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), we also investigated the interface between the formed LiF films and a mixture of PEO+LiTFSI by X-ray photoelectron spectroscopy (XPS), showing decomposition of the LiTFSI at the interface.
  • Thumbnail Image
    ItemOpen Access
    PEO infiltration of porous garnet-type lithium-conducting solid electrolyte thin films
    (2021) Waidha, Aamir Iqbal; Vanita, Vanita; Clemens, Oliver
    Composite electrolytes containing lithium ion conducting polymer matrix and ceramic filler are promising solid-state electrolytes for all solid-state lithium ion batteries due to their wide electrochemical stability window, high lithium ion conductivity and low electrode/electrolyte interfacial resistance. In this study, we report on the polymer infiltration of porous thin films of aluminum-doped cubic garnet fabricated via a combination of nebulized spray pyrolysis and spin coating with subsequent post annealing at 1173 K. This method offers a simple and easy route for the fabrication of a three-dimensional porous garnet network with a thickness in the range of 50 to 100 µm, which could be used as the ceramic backbone providing a continuous pathway for lithium ion transport in composite electrolytes. The porous microstructure of the fabricated thin films is confirmed via scanning electron microscopy. Ionic conductivity of the pristine films is determined via electrochemical impedance spectroscopy. We show that annealing times have a significant impact on the ionic conductivity of the films. The subsequent polymer infiltration of the porous garnet films shows a maximum ionic conductivity of 5.3 × 10-7 S cm-1 at 298 K, which is six orders of magnitude higher than the pristine porous garnet film.
  • Thumbnail Image
    ItemOpen Access
    Recycling of all‐solid‐state Li‐ion batteries : a case study of the separation of individual components within a system composed of LTO, LLZTO and NMC
    (2023) Waidha, Aamir Iqbal; Salihovic, Amila; Jacob, Martine; Vanita, Vanita; Aktekin, Burak; Brix, Kristina; Wissel, Kerstin; Kautenburger, Ralf; Janek, Jürgen; Ensinger, Wolfgang; Clemens, Oliver
    With the current global projection of over 130 million electric vehicles (EVs), there soon will be a need for battery waste management. Especially for all‐solid‐state lithium‐ion batteries (lithium ASSBs), aspects of waste management and circular economy have not been addressed so far. Within such ASSBs, the use of solid‐electrolytes like garnet‐type Li6.5La3Zr1.5Ta0.5O12 (LLZTO) may shift focus on strategies to recover not only the transition metal elements but also elements like La/Zr/Ta. In this work, we present a two‐step recycling approach using citric acid as the leaching agent to separate and recover the individual components of a model cell comprising of Li4Ti5O12 (LTO) anode, Li6.5La3Zr1.5Ta0.5O12 (LLZTO) garnet electrolyte and LiNi1/3Mn1/3Co1/3O2 (NMC) cathode. We observe that by adjusting the concentration of citric acid, it was possible to separate the materials from each other without strong mixing of individual phases and also to maintain their principle performance characteristics. Thus, the process developed has a potential for upscaling and can guide towards considering separation capability of battery components in the development of lithium ASSBs.