2D/1D nanocomposites for energy storage applications

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The aim of this research proposal is to prepare and to study hybrid electrodes of one- and two-dimensional (1D/2D) nanomaterials for energy storage applications, such as Li/Na-ion batteries.To this end, liquid phase exfoliation of transition metal hexathio- and hexaseleno-diphosphates (2D) is going to be performed in inert gas conditions. The resulting dispersion will be size-selected by reported centrifugation techniques which will enable to prepare composites of different sizes of the 2D nanomaterial with carbon nanotubes (1D). For a competitive use of nanomaterials or nanocomposites in device applications, it will be necessary to understand and to exploit synergistic effects between the individual compounds. Systematic studies on the different impacts on the electrode performance such as i.a., the nanoparticle size and thickness, 1D/2D mixing ratio, intercalation compound, will be required in order to rationalise the development of high-performance electrodes.For this purpose, different mixing ratios between the 1D and 2D nanomaterial have to be tested for different sizes and thicknesses of the 2D nanoplatelets in order to study geometric impacts on the 1D/2D interaction. Such studies are going to be implemented on a model system (Ni2P2S6), which was analysed by the applicant in previous exfoliation experiments. The fabricated anodes will be implemented in experimental Li- and Na-ion battery full cells and characterised by microscopy and spectroscopy, as well as mechanically and electronically before and after charge/discharge cycle experiments, respectively.Such experiments will enable to separate material decomposition occurring upon processing from effects arising from device operation, which will be helpful for optimisation of the electrode architecture, as well as for identification and prevention of effects that promote the material degradation.The knowledge gained from these results will be used to implement and study other M2P2Ch6 (M = transition metal, Ch = chalcogenide) species in energy storage devices. While for other compounds, similar tedious measurements have to be performed as for the Ni2P2S6 electrodes, the full characterisation is important for a solid benchmarking and to further study and understand the impacts of different material properties on the intercalation chemistry and thus the electrode performance of this unique isomorphous material systems. This will allow to rationally identify ideal candidates for novel high-performance nanocomposite electrodes.The experiments performed in inert gas conditions will be repeated in ambient conditions in order to study the stability of the electrodes in realistic and industrially relevant processing conditions, which will give deeper insights into degradation processes and enable to find strategies how to prevent them.To this end, it will be important to study the electrode morphology, chemical composition and performance before and after charge cycles, respectively.