Advanced Materials for Energy Conversion and Storage: Functional Materials II
Sponsored by: TMS Functional Materials Division, TMS: Energy Conversion and Storage Committee
Program Organizers: Amit Pandey, LG Fuel Cell Systems Inc.
Thursday 8:30 AM
March 2, 2017
Location: San Diego Convention Ctr
Session Chair: Reza Shahbazian-Yassar, University of Illinois at Chicago; Paul Ohodnicki, NETL
8:30 AM Invited
Free the Electron: Mitigating Polaronic Bottlenecks in Cathode Materials: Sarbajit Banerjee1; 1Texas A&M University
Limitations to the power and energy densities of Li-ion batteries constitute a major impediment to our energy future. The development of novel battery architectures and new battery chemistries is imperative to address this challenge. In recent work, we have used V2O5 as a model system to seek atomistic understanding of lithiation/delithiation pathways. Scanning transmission X-ray microscopy studies in conjunction with density functional theory suggest that polaron localization plays a key role in limiting cation mobility, giving rise to heterogeneous lithiation across individual cathode particles. As a means of circumventing polaron localization, metastable polymorphs accessible from topochemical synthesis represent a particularly useful set of compounds. I will discuss some recently discovered metastable phases that allow for unprecedented Li-ion and even multivalent cation mobility. These compounds represent particularly excellent examples of the concept of “frustrated coordination” and mitigate polaron confinement by dint of greater degeneracy of orbitals at the conduction band edge.
Increasing Ionic Conductivity with Highly Ionizing Radiation: Jacob Shamblin1; Cameron Tracy2; Rodney Ewing2; Joshua Sangoro1; Caitlin Taylor1; Maulik Patel1; William Weber1; Raul Palomares1; Eric O'Quinn1; Maik Lang1; 1The University of Tennessee; 2Stanford University
Many complex oxides exhibiting the pyrochlore structure display ionic conductivity on the order of yttria-stabilized zirconia and thus find use as potential electrolytes in solid oxide fuel cells. Here we present a new strategy for further increasing ionic conductivity through irradiation with heavy ions of high specific energy (> 5 MeV/u). Select pyrochlore compositions (e.g., Gd2Ti2O7, Gd2Zr2O7 and Er2Ti2O7) have been irradiated at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany. Radiation-induced phase transformations include amorphization, disordering to a fluorite-type phase, and a combination of the two. Broadband dielectric spectroscopy measurements reveal that ionic conductivity in these far-from-equilibrium phases (which are stable up to about 800 C) is in some cases increased by a factor of 250 compared with the ordered pyrochlore phase prior to irradiation. This increase is due to enhanced mobility in the irradiated phases as well as an increased defect concentration.