Electronic structure descriptor for narrow-band red phosphors

Congratulations to Zhenbin on his first paper “Electronic Structure Descriptor for Discovery of Narrow-Band Red-Emitting Phosphors” in Chemistry of Materials! Narrow-band red-emitting phosphors are a critical component in phosphor-converted light-emitting diodes for highly efficient illumination-grade lighting. In this work, we report the discovery of a quantitative descriptor for narrow-band Eu2+-activated emission identified through a comparison of the electronic structure of known narrow-band and broad-band phosphors. By incorporating this descriptor in a high throughput first principles screening of 2,259 nitride compounds, we identify five promising new nitride hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit good chemical stability, thermal quenching resistance and quantum efficiency, as well as narrow-band emission.

Insights into the Li7P3S11 superionic conductor

Iek-Heng Chu just published a new article in ACS Applied Materials & Interfaces. This is a highly collaborative work involving the expertise of many MAVRL group members as well as the Meng group. In this work, we investigate the performance limits of Li7P3S11, a highly promising lithium superionic conductor solid electrolyte. We find that Li7P3S11 is metastable at 0 K but becomes stable at above 630 K (∼360°C) when vibrational entropy contributions are accounted for, in agreement with differential scanning calorimetry measurements. Both scanning electron microscopy and the calculated Wulff shape show that Li7P3S11 tends to form relatively isotropic crystals. In terms of electrochemical stability, first-principles calculations predict that, unlike the LiCoO2 cathode, the olivine LiFePO4 and spinel LiMn2O4 cathodes are likely to form stable passivation interfaces with the Li7P3S11 SCE. This finding underscores the importance of considering multicomponent integration in developing an all-solid-state architecture. We also find that the AIMD-predicted room-temperature Li+ conductivity of 57 mS/cm is much higher than the experimental values suggesting the potential for further optimization.

Prof Ong is an awardee of the 2016 ONR Young Investigator Program

Professor Ong has been selected as one of the 2016 recipients for the ONR Young Investigator Program (YIP) Award. This award seeks to identify and support academic scientists and engineers who are in their first or second full-time tenure-track or tenure-track-equivalent academic appointment and who show exceptional promise for doing creative research. The program’s objectives are to attract outstanding faculty members to the Department of Navy’s research program, to support their research, and to encourage their teaching and research careers.

Thermodynamics and kinetics of multi-electron ε-VOPO4

Paul Lin published his first-author paper on the “Thermodynamics, Kinetics and Structural Evolution of ε-LiVOPO4 over Multiple Lithium Intercalation”in Chemistry of Materials, as well as his co-author paper in ACS Applied Materials & Interfaces on “Thermal Stability and Reactivity of Cathode Materials for Li-Ion Batteries”. These papers are collaborative work as part of the NorthEast Center for Chemical Energy Storage and focuses on multi-electron rechargeable battery cathodes that have the potential to yield much higher energy densities than traditional single-electron chemistries.

Role of Na dopants on conductivity of cubic Na3PS4

Congratulations to Zhuoying on her first paper in Chemistry of Materials title “Role of Na+ Interstitials and Dopants in Enhancing the Na+ Conductivity of the Cubic Na3PS4 Superionic Conductor”. In this work, we studied the effect of Na+ interstitials on the stability and ionic conductivity in the highly promising cubic Na3PS4 superionic conductor. We find that dopants significantly enhance the Na+ ionic conductivity and predict that Sn4+ doping may yield higher conductivities than previously achieved. The other authors are Iek-Heng Chu and Zhi Deng.

Elastic properties of alkali superionic conductors

Zhi Deng, Zhenbin Wang and Iek-Heng Chu have just published their paper on “Elastic Properties of Alkali Superionic Conductor Electrolytes from First Principles Calculations” in the Journal of the Electrochemical Society. This work examines the elastic properties of ceramic alkali superionic conductor that are of interest in enabling safer, more energy dense all-solid-state batteries. Elastic properties have a critical influence on the fabrication, operation, and design of a battery.

Design principles for solid-state lithium superionic conductors

Prof Ong is a co-author on a new paper on “Design principles for solid-state lithium superionic conductors” just been published in Nature Materials! This work reveal a fundamental relationship between anion packing and ionic transport in fast Li-conducting materials and expose the desirable structural attributes of good Li-ion conductors, and provide important insight towards the understanding of ionic transport in Li-ion conductors.