Dr. Meng GU is now an Associate Professor in the Department of Materials Science and Engineering in the Southern University of Science and Technology. His team is specialized in the probing the structure-property relationship of energy-related materials using in-situ/aberration-corrected scanning transmission electron microscopy. Meng Gu received his Ph.D. degree (2011) in materials science in the University of California Davis. After joining EMSL in Pacific Northwest National Laboratory, his research focused on the study of energy materials including batteries materials and catalysts. Dr. Gu joined Dow Corning/Dow Chemical in Michigan as a core R&D materials scientist in February 2014 focusing on the development of industrial catalysts, and advanced microscopy analysis of reactions. He has 108 peer-reviewed journal publications including Energy & Environmental Science, Nature Communications, Physical Review Letters, Nano Letters, Journal of Materials Chemistry A, Advanced Materials, ACS nano, Angewandte Chemie, Nano Energy, ACS catalysis, Chemistry of Materials, Applied Physics Letters, Ultramicroscopy, Journal of Electrochemical Society, and etc. His publications have been cited more than 7000 times, and are highlighted by U.S. DOE, PNNL, SLAC national lab, London Center for Nanotechnology, Imperial College London and other social media. Dr. Gu has been awarded the Albert CREWE award from the Microscopy Society of America in Aug 2nd 2015 for his outstanding research.
Project I: In-situ Transmission electron microscopy analysis of secondary ion batteries
Schematic of nano-battery experiments inside a TEM. The setup of in-situ TEM open cell using ionic liquid as electrolyte (a); open cell approach using Li2O as solid electrolyte (b); and liquid cell approach (c) (Gu et al, Nano Lett., 2013, 13 (12), pp 6106–6112)
Description: In situ transmission electron microscopy (TEM) studies of lithium ion batteries using an open-cell configuration have helped us to gain fundamental insights into the structural and chemical evolution of the electrode materials in real time. We have creatively applied in-situ TEM analysis to the study of anode materials such as Si-C composite, Si-conductive polymer composite, Ge, TiO2, Li4Ti5O12, SnO2, etc in Li-ion and Na-ion batteries. Novel functional/failure mechanism of these materials are revealed as a result. Furthermore, We have developed an open-cell technique to allow atomic scale characterization of the detailed phase evolution of electrode materials in real time. The reaction mechanism between the intercalation process and conversion reaction are made clear by atomic scale imaging.
In addition, we developed an operando TEM electrochemical liquid cell to see solid electrolyte interphase layer, providing the configuration of a real battery and in a relevant liquid electrolyte. we also discovered new insights different from the open cell configuration—the dynamics of the electrolyte and, potentially, a future quantitative characterization of the solid electrolyte interphase layer formation and structural and chemical evolution.
Project II: Investigation of novel nano-structures for Li-ion and all solid state batteries
Description: Maximizing the usage of renewable energy will reduce our reliance on dwindling natural resources and environmental pollution. Batteries are an important enabling technology for renewable energy, portable electronics, and modern transportation systems such as hybrid electric vehicles. However, limitation of current materials has to be overcome if long-life and low-cost batteries are to be built. The establishment of my research focusing on advanced characterization of lithium batteries aligns well with this need of modern technology and with the goals of the energy storage research. We have successfully demonstrated the superior cycling performance of anode materials, such as mesoporous Si foam, mesoprous Si hollow spheres, Si-C yolk-shell, Si-conductive polymer. In addition, we successfully identified the failure mechanism of Li-rich layered cathode materials and improved their performance by controlling the synthesis conditions and apply AlF3 coatings.
Going beyond traditional Li-ion batteries, we focus on all solid state batteries. All-solid-state batteries present us with opportunities of designing safer energy storage devices with high voltage and long cycle life for ultrathin electronics, implantable medical devices, smart windows, and even electric vehicles. Currently, the all-solid-state Li-ion batteries are fabricated using thin film deposition methods, of which the magnetron sputtering/atomic layer deposition/pulsed laser deposition growth of Li-containing thin film materials shows great advantage for all-solid-state batteries study and fabrication. As shown in the figure below, the 2D all-solid-state batteries can greatly reduce the thickness of electrolyte and electrodes, enhancing the power density. In addition, the 3D design of the all-solid-state batteries utilizes sufficiently high surface area, which allows for high power density and high volumetric energy density.
Schematic of 2D (a) and 3D design of All-Solid-State batteries
Project III: Heterogeneous Catalysts Synthesis and in-situ TEM Analysis
We are actively finding out better catalysts for waste water treatment, waste gas conversion, hydrogen production, bio-mass conversion to diesel, etc. We investigate interesting core-shell bi-metallic catalysts, single atom/site catalyst, and emphasize the bonding between the dispersed catalyst ions and matrix materials. With our in-situ Environmental-TEM capability, we can create a reaction chamber inside a TEM, which allow us directly visualize the changes/dynamics of the catalysts at the atomic-scale in high temperature and certain gas environment.
Project IV: Development of 3-D chemical imaging technique
Example: 3D EDS tomography showing the distribution of Mn and Ni in Li1.2Ni0.2Mn0.6O2
Description: A variety of approaches are being made to enhance the performance of lithium ion batteries. Incorporating multivalence transition-metal ions into metal oxide cathodes has been identified as an essential approach to achieve the necessary high voltage and high capacity. However, the fundamental mechanism that limits their power rate and cycling stability remains unclear. The power rate strongly depends on the lithium ion drift speed in the cathode. We found that during cathode synthesis and processing before electrochemical cycling in the cell nickel can preferentially move along the fast diffusion channels and selectively segregate at the surface facets terminated with a mix of anions and cations. This segregation essentially can lead to a higher lithium diffusion barrier near the surface region of the particle. Therefore, it appears that the transition-metal dopant may help to provide high capacity and/or high voltage but can be located in a “wrong” location that may slow down lithium diffusion, limiting battery performance.
Project V: Interface Physics Study at an epitaxial metal/oxide or oxide/oxide heterojunction
This project involves the development of next generation spintronic devices, sensors, and low temperature solid oxide fuel cells requires the development of materials with new functional properties not found in conventional bulk materials. A novel route involves harnessing the unexpected physical phenomena that result from the changes in structure and chemistry which occur over nanometer length scales at surfaces and interfaces. The approach of this work utilizes MBE/laser-assisted growth to control interfacial properties with atomic layer precision in combination with state-of-the-art techniques for characterizing the structural and chemical properties. In this way, a full understanding of the origins of new magnetic and electronic properties derived from interfacial mechanisms can be determined.
We use STEM and EELS and Z contrast image to observe the interface of the superlattice and investigate the structure, the distribution of different atoms and the vacancy of oxygen atoms. The thin film and heterostructures produced are ideally suited for analysis using scanning transmission electron microscopy (STEM). The advantages of STEM over other characterization techniques lies in the ability to combine high angle annular dark field Z contrast imaging with electron energy loss spectroscopy (EELS), thus creating a probe of the local chemical structure across hetero- interfaces with nearly atomic level precision. These EELS spectra have the capability to probe effects such as valence and polar discontinuities, which have been proposed to cause surface and interface phenomena, such as electric conductivity and magnetic property change. Then comes clearly the relationship between structure and property of the thin films
Teaching at SUSTech
Instruments and Group Members at SUSTech
Electron microscopy Pico-center @SUSTech house the most advanced instruments including double Cs-corrected&Mono FEI Themis with super-X EDS and Quantum EELS; Cs-corrected Environmental TEM, Talos with Super-X EDS; and F-30 S/TEM
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