All-solid-state lithium ion batteries (ASSLIBs) with high energy density are promising to substitute the liquid organic electrolyte based batteries, which enable more compact stacking structure and increased safety of next-generation high-energy density batteries and power devices, e.g., electric vehicles. However, the interfacial compatibility between electrodes and electrolyte is still one of the biggest challenges for applying solid electrolytes in ASSLIBs. Therefore, we not only devote ourselves to screening superionic conductors for ASSLIBs based on DFT calculations, but also understanding the interfacial transport mechanism at atomic and electronic levels for the advanced design of the compatible interfaces for the next-generation ASSLIBs.
New Design Principles for Advanced Catalysts
As a promising avenue for small to intermediate scale operations, fuel cell devices play a vital role in energy generation and utilization technologies. However, the slow kinetics of oxygen reduction reaction (ORR) as the critical step of electrochemical oxidation of a fuel (typically hydrogen, methanol, etc.) limits the development of fuel cell devices. The classical volcano relationship on the basis of the two- and four-electron oxygen reduction pathways proposed by Nørskov demonstrates limited success in bringing down the ORR over potential. Thus, we are especially interested in finding a new strategy to break the traditional volcano relationship and design catalysts superior to platinum by combing high-throughput simulations, materials physics, chemistry and experiment.
Layered Thermoelectric Materials Design
Thermoelectric (TE) materials with the ability to convert temperature differences to electric voltage and high chemical stability can be used in power generations from waste heat or in extreme conditions such as the outer space. Recently, a group of phonon glass-electron crystal (PGEC) with layered structure has been reported with ultra-low thermal conductivity and decent power factor. However, the discovery and improvement of this group of materials is limited by the long and costy process to synthesize, optimize and measure thermoelectric properties. Here, we perform a comprehensive study on the stability and thermoelectric performance of thousands of layered TE materials, and uncover the design principles for promising PGEC TE materials, based on high throughout density functional theory (DFT) calculations and machine learning.
Improving The Stability of Perovskite Solar Cells
Hybrid organic-inorganic Perovskite is recently thought as the 3rd new generation solar cell for its competitive power conversion efficiency and low cost fabrication, while the instability is one of the main obstacles for being widely used in the photovoltaic field. Thus, we focus on improving the intrinsic stability of perovskite by chemistry and structural modification and understanding the correlation between phase stability and intrinsic atomistic level features. We aslo collaborate with the leading experimental group at SJTU.
Wu, J.; Qi, W.; Luo, Z.; Liu, K.; Zhu, H., Electronic Structure and Stability of Lead-free Hybrid Halide Perovskites: A Density Functional Theory Study. Journal of Shanghai Jiaotong University (Science) 2018, 23, (1), 202-208. pdf
Structural Materials
High-throughput Simulations on Generalized Stacking Fault Energies
The dislocation core structures and mobilities are partly controlled by the ease to shear a crystal along a given crystallographic plane, which can be characterized by the generalized stacking fault energy (GSFE). Thus, the determination of GSFE appears to be an instructive first step towards the understanding of the plasticity of materials. However, the success of such complex GSFE calculations usually relied heavily on the human intuition and manual operations on the atomic model building, simulation parameter adjustments, and final results analysis, which make it difficult for large-scale investigation of GSFEs of a variety of metals. Therefore, we focus on developing a high-throughput tool for calculating GSFE on typical slip systems of HCP, FCC and BCC structure metals based on density functional theory (DFT) simulations, and applying it to create the GSFE database for the elemental Materials.
As the lightest structural materials with high specific strength, Mg has the potential to be used in auto-mobile industries and aerospace fields. However the poor corrosion and ductility of Mg alloys limit their wide applications. In this project, we focus on two aspects: (1) determining the polarization curves for Mg alloys and their thermodynamic stability in aqueous environment based on DFT simulations and experimental data to understand different alloying elements’ effects; (2) studying the structure, electronic property and mechanical strength of Mg alloy matrix and precipitations. We are also interested in the properties of other important interfaces, for example the Ni-Ni3Al interface design through appropriate alloyings.