Yuh-chieh Lin and Iek-Heng Chu are proud co-authors of a recent article published in Advanced Energy Materials on KVOPO4, a novel, high capacity multi-electron cathode for Na-ion batteries. This highly collaborative work, which is part of the NorthEast Center for Chemical Energy Storage (NECCESS) demonstrates fully activated Na+ intercalation over the V3+/4+/5+ couple in a vanadyl phosphate phase for the first time, with a high practical energy density of over 600 Wh/kg, the highest yet reported for any sodium cathode material. DFT calculations (contribution from MAVRL) shows that KVOPO4 is a 3D ionic conductor with low Na+ migration energy barrier of
Hanmei’s co-author paper with the Chen and Lipomi groups on “Understanding the Electrochemical Properties of Naphthalene Diimide: Implication for Stable and High-Rate Lithium-Ion Battery Electrodes” has just been published in Chemistry of Materials. In this work, we investigate the redox-active organic molecule, 1,4,5,8-naphthalenediimide (NDI), as a low-cost, high-abundance alternative to transition metal-based electrodes for lithium-ion batteries. Hanmei’s contribution is in using the latest SCAN functional combined with the HSE functional to identify the stable Li intercalation sites and compute the voltage profile of NDI, which are in excellent agreement with the experiments from the Chen group.
We are proud to be part of a collaborative publication with the Laboratory of Energy Storage and Conversion on “New Insights into the Interphase between the Na Metal Anode and Sulfide Solid-State Electrolytes: A Joint Experimental and Computational Study” published in ACS Applied Materials & Interfaces. This combined experimental and computational study shows that capacity fade is primarily brought about by the reaction between the Na anode and Na solid electrolytes such as Na3SbS4, Na3PS4, and Cl-doped Na3PS4, and demonstrates techniques that can be used to identify the interfacial products. Read the article here!
Chen’s paper on “Automated generation and ensemble-learned matching of X-ray absorption spectra” has been published in npj Computational Materials. In this work, we developed XASdb, a large database of computed reference X-ray absorption spectra (XAS), and a novel Ensemble-Learned Spectra IdEntification (ELSIE) algorithm for the matching of spectra. XASdb currently hosts more than 800,000 K-edge X-ray absorption near-edge spectra (XANES) for over 40,000 materials from the open-science Materials Project database. We will demonstrate that the ELSIE algorithm, which combines 33 weak “learners” comprising a set of preprocessing steps and a similarity metric, can achieve up to 84.2% accuracy in identifying the correct oxidation state and coordination environment. The XASdb with the ELSIE algorithm has been integrated into a web application in the Materials Project, providing an important new public resource for the analysis of XAS to all materials researchers. Finally, the ELSIE algorithm itself has been made available as part of Veidt, an open source machine learning library for materials science.
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Iek-Heng Chu’s paper on “Predicting the Volumes of Crystals” has been published in Computational Materials Science. In this collaborative work with the Hacking Materials group, we developed two schemes for predicting crystal volumes. Accurate crystal volume estimates are immensely useful for further experimental analysis, or to generate initial guesses for electronic structure optimizations. The volume prediction algorithms are implemented in the open-source pymatgen software.
Hui Zheng is a co-author on a recently published article in Physical Review Letters on “First-Order Interfacial Transformations with a Critical Point: Breaking the Symmetry at a Symmetric Tilt Grain Boundary”. A collaboration with the Luo group, this work examines symmetry breaking in the ∑5 (210) GB using a modified genetic algorithm with Monte Carlo and molecular dynamics simulations. Read more about this work here.
Our paper on “Mining Unexplored Chemistries for Phosphors for High-Color-Quality White-Light-Emitting Diodes” has been published in Joule. Using supercomputers and data mining, we identified Sr2LiAlO4, the first known Sr-Li-Al-O quaternary crystal, as a highly promising phosphor material in low-cost, high-color-quality white LEDs. Eu2+ and Ce3+-activated Sr2LiAlO4 phosphors exhibit broad green-yellow and blue emissions, respectively, with excellent thermal quenching resistance of > 88% intensity at 150oC. A prototype phosphor-converted white LED utilizing Sr2LiAlO4-based phosphors yields an excellent color rendering index exceeding 90. This work is a collaboration between the Materials Virtual Lab (UCSD), McKittrick group (UCSD) and Im group (Chonnam University). The lead authors are Zhenbin Wang, Jungmin Ha and Yoon Hwa Kim. More information about this work can be found in the Jacobs School of Engineering News as well as Science Daily, Phys.org, etc.
Hui Zheng’s first paper on “Role of Zr in strengthening MoSi2 from density functional theory calculations” has just been published in Acta Materialia. MoSi2 is an important intermetallic with excellent oxidation resistance at high temperatures. However, “pesting” by oxygen limits its application at intermediate temperatures. Using DFT calculations, we show that Zr nanoparticles act as a getter for oxygen, and in the process, significantly strengthens MoSi2 interfaces and grain boundaries. We also use the Materials Project to efficiently screen for other potential getter elements using simple thermodynamic descriptors, a general approach that can be extended to other alloy systems of interest.
Hanmei’s first paper on “Probing Solid-Solid Interfacial Reactions in All-Solid-State Sodium-ion Batteries with First Principles Calculations” has just been published in Chemistry of Materials. In this comprehensive work, we show how explicit AIMD models can lead to different predictions of interfacial reaction products from simple thermodynamic approximations. Specifically, SO4 formation is predicted to be favored over PO4 formation at the interface between NaCoO2 and Na3PS4. We also identified several promising new candidates for buffer materials that potentially show lower reactivity with common electrodes and solid electrolytes.