Kavli Affiliate: Scott K. Cushing
| First 5 Authors: Kim H. Pham, Scott K. Cushing, , ,
| Summary:
Superionic conductors, or solid-state ion-conductors that surpass 0.01 S/cm
in conductivity, can enable more energy dense batteries, robust artificial ion
pumps, and optimized fuel cells. However, tailoring superionic conductors
require precise knowledge of ion migration mechanisms that are still not well
understood, due to limitations set by available spectroscopic tools. Most
spectroscopic techniques do not probe ion hopping on its inherent picosecond
timescale, nor the many-body correlations between the migrating ions, lattice
vibrational modes, and charge screening clouds–all of which are posited to
greatly enhance ionic conduction. Here, we develop an ultrafast technique that
measures the time-resolved change in impedance upon light excitation which
triggers selective ion-coupled correlations. We apply our proposed technique to
study a solid-state Li+ conductor Li0.5La0.5TiO3 (LLTO). We compare the
relative change in impedance of LLTO before and after a UV to THz frequency
excitation to map the corresponding ion-many-body-interaction correlations. We
also develop a cost-effective, non-time-resolved laser-driven impedance method
that is more accessible for lab-scale adoption. From both our techniques, we
determine that electronic screening and phonon-mode interactions dominate the
ion migration pathway of LLTO. Although we only present one case study, our
technique can also probe O2-, H+, or other ion and charge carrier transport
phenomena where ultrafast correlations control transport. Furthermore, the
temporal relaxation of the measured impedance can distinguish ion transport
effects caused by many-body correlations, optical heating, correlation, and
memory behavior.
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