Yanzhou Ji

Interdiffusion across solid electrolyte-electrode interface

A phase-field model is developed for studying the cation interdiffusion across electrolyte-electrode interfaces in solid oxide fuel cell (SOFC) that can be contributing to long timescale performance degradation. Demonstrated on an interface between an 8%molY2O3-stabilized ZrO2 and a La0.65Sr0.3MnO3−x typically used in SOFC, time-dependent evolution of the cation interdiffusion profiles are predicted by linking the phase-field model to a diffusion equation. The simulated interdiffusion profiles agree with independent experimental data in both time and space domains at different temperatures.

Phase-Field Based Multiscale Modeling of Heterogeneous Solid Electrolytes: Applications to Nanoporous Li3PS4

Modeling the effective ion conductivities of heterogeneous solid electrolytes typically involves the use of a computer-generated microstructure consisting of randomly or uniformly oriented fillers in a matrix. However, the structural features of the filler/matrix interface, which critically determine the interface ion conductivity and the microstructure morphology, have not been considered during the microstructure generation. Using nanoporous β-Li3PS4 electrolyte as an example, we develop a phase-field model that enables generating nanoporous microstructures of different porosities and connectivity patterns based on the depth and the energy of the surface (pore/electrolyte interface), both of which are predicted through density functional theory (DFT) calculations. Room-temperature effective ion conductivities of the generated microstructures are then calculated numerically, using DFT-estimated surface Li-ion conductivity (3.14 × 10-3 S/cm) and experimentally measured bulk Li-ion conductivity (8.93 × 10-7 S/cm) of β-Li3PS4 as the inputs. We also use the generated microstructures to inform effective medium theories to rapidly predict the effective ion conductivity via analytical calculations. When porosity approaches the percolation threshold, both the numerical and analytical methods predict a significantly enhanced Li-ion conductivity (1.74 × 10-4 S/cm) that is in good agreement with experimental data (1.64 × 10-4 S/cm). The present phase-field based multiscale model is generally applicable to predict both the microstructure patterns and the effective properties of heterogeneous solid electrolytes.

Topological dynamics of vortex-line networks in hexagonal manganites

Three-dimensional vortex structures and dynamics in hexagonal manganites Fei Xue, Nan Wang, Xueyun Wang, Yanzhou Ji, Sang-Wook Cheong, and Long-Qing Chen Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA *Corresponding author: lqc3@psu.edu