Category: Publications

Publications

Effect of transition metal mixing in Layered P2 Oxides

Our work on “Effects of Transition-Metal Mixing on Na Ordering and Kinetics in Layered P2 Oxides” has just been published in Physical Review Applied. In this work by Chen Zheng and other co-authors, we systematically investigate the effects of transition-metal (TM) mixing on Na ordering and kinetics in the NaxCo1−yMnyO2 model system using DFT calculations. We show that the TM composition at the Na(1) (face-sharing) site has a strong influence on the Na site energies, which in turn impacts the kinetics of Na diffusion towards the end of the charge. By employing a site-percolation model, we establish theoretical upper and lower bounds for TM concentrations based on their effect on Na(1) site energies, providing a framework to rationally tune mixed-TM compositions for optimal Na diffusion.

Publications

Divalent-doped NASICON with high Na+ conductivity

Our work on “Divalent-doped Na3Zr2Si2PO12 Natrium Superionic Conductor: Improving the ionic conductivity via simultaneously optimizing the phase and chemistry of the primary and secondary phases” has just been published in the Journal of Power Sources. In this work co-first-authored by Mojitaba Samiee (Luo group) and Balachandran Radhakrishnan (Ong group), we show that divalent dopants with low solubility in NASICON lead to the formation of a conducting secondary phase, thereby improving the grain boundary conductivity compared to undoped NASICON. Concurrently, the introduction of divalent dopants is accompanied by a change in the Si/ P ratio in the primary NASICON bulk phase, transforming monoclinic NASICON to rhombohedral NASICON. NASICON chemistries with significantly improved and optimized total ionic conductivity of 2.7 mS/cm have been synthesized. This work suggests a new general direction to improve the ionic conductivity of solid electrolytes via simultaneously optimizing the primary bulk phase and the microstructure (including grain boundary segregation and secondary phases).

Publications

Goodbye to Bala

This week, we say goodbye to our very first alumni, Bala. We wish Bala all the best in his new post at NASA, and look forward to his future discoveries and success as a researcher!

Publications

New Li3Y(PS4)2 and Li5PS4Cl2 Superionic Conductors

Zhuoying’s first author paper on “Li3Y(PS4)2 and Li5PS4Cl2, New Lithium Superionic Conductors Predicted from Silver Thiophosphates using Efficiently Tiered Ab Initio Molecular Dynamics Simulations” has just been published in Chemistry of Materials (Special Issue on High-Throughput Functional Materials Discovery). In this work, we propose two new lithium superionic conductors, Li3Y(PS4)2 and Li5PS4Cl2, that are predicted to have excellent ionic conductivity and potentially better stability at the interfaces compared to current state-of-the-art superionic conductors. We welcome experimental researchers to attempt synthesis of these compounds and validation of our predictions!

Publications

Structure-Property-Composition Relations in β-SiAlON:Eu2+ Phosphor

Our work on “Elucidating Structure–Composition–Property Relationships of the β-SiAlON:Eu2+ Phosphor” has been published in Chemistry of Materials. Using first-principles calculations, we identified and confirmed various chemical rules for Si−Al, O−N, and Eu activator ordering in β-SiAlON, one of the most promising narrow-band green phosphors for high-power light-emitting diodes and liquid crystal display backlighting with wide color gamut. Through the construction of energetically favorable models based on these chemical rules, we studied the effect of oxygen content and Eu2+ activator concentrations on the local EuN9 activator environment, and its impact on important photoluminescence properties such as emission peak position (using the band gap as a proxy), bandwidth, and thermal quenching resistance.  Based on these insights, we discuss potential strategies for further composition optimization of β-SiAlON.

Publications

Thermodynamic scale of inorganic crystalline metastability

Prof Ong is a co-author on a recent article in Science Advances on the thermodynamic scale of inorganic crystalline metastability. This article uses the Materials Project, its API and pymatgen to perform a large-scale data-mining study of the thermodynamic scale of metastability for 29,902 observed inorganic crystalline phases. Press release is available on EurekAlert.

Publications

Room-Temperature All-solid-state Na-ion Batteries with Cl-doped Na3PS4

In collaboration with the Laboratory of Energy Storage and Conversion (LESC), we have developed a room-temperature all-solid-state rechargeable sodium-ion battery utilizing a novel Cl-doped Na3PS4 superionic conductor. The Cl-doped tetragonal Na3PS4 solid electrolyte exhibits room-temperature Na+ conductivity exceeding 1 mS/cm, and an all-solid-state TiS2/t-Na3−xPS4−xClx/Na cell utilizing this solid electrolyte can be cycled at room-temperature at a rate of C/10 with a capacity of about 80 mAh/g over 10 cycles. We show that this excellent electrochemical performance is not only due to the high Na+ conductivity of the solid electrolyte, but also due to the effect that “salting” Na3PS4 has on the formation of an electronically insulating, ionically conducting solid electrolyte interphase. This work is published in Scientific Reports. The co-first authors are Iek-Heng Chu (MAVRL), Christopher S. Kompella (LESC) and Han Nguyen (LESC), and the corresponding authors are Professors Shirley Meng and Shyue Ping Ong.

Publications

Data-driven Methods for the Study and Design of Alkali Superionic Conductors

Our article on “Data-driven First Principles Methods for the Study and Design of Alkali Superionic Conductors” has been published in  Chemistry of Materials as part of an invited Methods and Protocols special topic. In this work, we provide a detailed exposition of the first principles techniques that can be used to design alkali superionic conductors, a topic of high current interest. Accompanying this article is a repository of well-documented Jupyter notebooks that allows any researcher to easily reproduce the analysis and apply the same techniques to other materials. The article is available online and the notebooks are available at the following Github repo.

Announcements, Publications

Crystalium released

We have published the world’s largest database of surface energies and Wulff shapes, dubbed Crystalium. A collaborative effort between the Materials Virtual Lab and the Materials Project, this new open-source database can help researchers design new materials for technologies in which surfaces and interfaces play an important role, such as fuel cells, catalytic converters in cars, computer microchips, nanomaterials and solid-state batteries. You can read more about it in the UCSD press release on EurekAlert! This work is published in Scientific Data as an open-access article, and Richard Tran, one of our undergraduate volunteers, is the first author.