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    Rolled-up tubes and cantilevers by releasing SrRuO 3-Pr 0.7Ca 0.3MnO 3 nanomembranes
    (New York, NY [u.a.] : Springer, 2011) Deneke, C.; Wild, E.; Boldyreva, K.; Baunack, S.; Cendula, P.; Mönch, I.; Simon, M.; Malachias, A.; Dörr, K.; Schmidt, O.G.
    Three-dimensional micro-objects are fabricated by the controlled release of inherently strained SrRuO 3/Pr 0.7Ca 0.3MnO 3/SrRuO 3 nanometer-sized trilayers from SrTiO 3 (001) substrates. Freestanding cantilevers and rolled-up microtubes with a diameter of 6 to 8 μm are demonstrated. The etching behavior of the SrRuO3 film is investigated, and a selectivity of 1:9,100 with respect to the SrTiO3 substrate is found. The initial and final strain states of the rolled-up oxide layers are studied by X-ray diffraction on an ensemble of tubes. Relaxation of the sandwiched Pr0.7Ca0.3MnO3 layer towards its bulk lattice parameter is observed as the major driving force for the roll-up of the trilayers. Finally, μ-diffraction experiments reveal that a single object can represent the ensemble proving a good homogeneity of the rolled-up tubes.
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    Free-standing Fe2O3 nanomembranes enabling ultra-long cycling life and high rate capability for Li-ion batteries
    (London : Nature Publishing Group, 2014) Liu, X.; Si, W.; Zhang, J.; Sun, X.; Deng, J.; Baunack, S.; Oswald, S.; Liu, L.; Yan, C.; Schmidt, O.G.
    With Fe2O3 as a proof-of-concept, free-standing nanomembrane structure is demonstrated to be highly advantageous to improve the performance of Li-ion batteries. The Fe2O3 nanomembrane electrodes exhibit ultra-long cycling life at high current rates with satisfactory capacity (808 mAh g-1 after 1000 cycles at 2 C and 530 mAh g-1 after 3000 cycles at 6 C) as well as repeatable high rate capability up to 50 C. The excellent performance benefits particularly from the unique structural advantages of the nanomembranes. The mechanical feature can buffer the strain of lithiation/delithiation to postpone the pulverization. The two-dimensional transport pathways in between the nanomembranes can promote the pseudo-capacitive type storage. The parallel-laid nanomembranes, which are coated by polymeric gel-like film and SEI layer with the electrolyte in between layers, electrochemically behave like numerous "mini-capacitors" to provide the pseudo-capacitance thus maintain the capacity at high rate.