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Doubling Reversible Capacities in Epitaxial Li4Ti5O12 Thin Film Anodes for Microbatteries
journal contribution
posted on 2019-04-22, 00:00 authored by Daniel
M. Cunha, Theodoor A. Hendriks, Alexandros Vasileiadis, Chris M. Vos, Tomas Verhallen, Deepak P. Singh, Marnix Wagemaker, Mark HuijbenDespite the lower
gravimetric capacity, Li4Ti5O12 is
an important alternative to graphite anodes, owing
to its excellent high temperature stability, high rate capability,
and negligible volume change. Although surfaces with lithium compositions
exceeding Li7Ti5O12 were observed
previously during the first charge–discharge cycles, no stable
reversible capacities were achieved during prolonged cycling. Here,
structural engineering has been applied to enhance the electrochemical
performance of epitaxial Li4Ti5O12 thin films as compared to polycrystalline samples. Variation in
the crystal orientation of the Li4Ti5O12 thin films led to distinct differences in surface morphology with
pyramidal, rooftop, or flat nanostructures for respectively (100),
(110), and (111) orientations. High discharge capacities of 280–310
mAh·g–1 were achieved due to significant surface
contributions in lithium storage. The lithiation mechanism of bulk
Li4Ti5O12 thin films was analyzed
by a phase-field model, which indicated the lithiation wave to be
moving faster along the grain boundaries before moving inward to the
bulk of the grains. The (100)-oriented Li4Ti5O12 films exhibited the highest capacities, the best rate
performance up to 30C, and good cyclability, demonstrating enhanced
cycle life and doubling of reversible capacities in contrast to previous
polycrystalline studies.
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Keywords
epitaxial Li 4 Ti 5 O 12lithiation wavevolume changeEpitaxial Li 4 Ti 5 O 12gravimetric capacityHigh discharge capacitiessurface contributionsDoubling Reversible CapacitiesLi 7 Ti 5 O 12surface morphologyLi 4 Ti 5 O 12 filmsFilm Anodescrystal orientationlithium storagebulk Li 4 Ti 5 O 12rate capabilitylithiation mechanismelectrochemical performancegraphite anodescycle life30 Cgrain boundariesLi 4 Ti 5 O 12temperature stabilityrate performancephase-field modellithium compositions