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Arteriovenous Metabolomics to Measure <em>In Vivo</em> Metabolite Exchange in Brown Adipose Tissue

Brown adipose tissue (BAT) plays a crucial role in regulating metabolic homeostasis through a unique energy expenditure process known as non-shivering ...

Sungkyunkwan University (SKKU)

The encapsulation of Ni-rich cathode materials (LiNiCoMnO) for lithium ion batteries in reduced graphene oxide (rGO) sheets is introduced to improve electrochemical performances. Using (3-aminopropyl)triethoxysilane, the active materials are completely wrapped with several rGO layers of ∼2 nm thickness. By virtue of the great electrical conductivity of graphene, the rGO-coated cathode materials exhibit much enhanced electrochemical performances of cycling property and rate capability. In addition, it is shown that the structural degradation of the active materials, which is from the rhombohedral layered structure (R3̅m) to the spinel (Fd3̅m) or rock-salt phase (Fm3̅m), is significantly reduced as well as delayed due to the protection of the active materials in the rGO layers from direct contact with electrolytes and the consequent suppression of side reactions.

Reduced Graphene Oxide-Wrapped Nickel-Rich Cathode Materials for Lithium Ion Batteries.

Tuning geometrical parameters of lithium-mixed transition-metal oxide (LiTM) cathode materials is a promising strategy for resource-efficient design of high-performance Li-ion batteries. In this paper, we demonstrate that simple and facile geometrical tailoring of the secondary microstructure of LiTM cathode materials without complex chemical modification or heterostructure engineering can significantly improve overall electrochemical performance of the active cathode materials. An optimized LiTM with a bimodal size distribution of primary particles inside the secondary particles exhibits a 53.8% increase in capacity at a high discharge rate (10 C) compared to a commercially available reference and comparable rate capability after 100 charge/discharge cycles. The key concept of this approach is to maximize the beneficial effects arising from the controlled sizes of primary particles. Multimodal/multiscale microscopic characterizations based on electron tomography and scanning transmission electron microscopy, combined with electron energy-loss spectroscopy and energy-dispersive X-ray spectroscopy from the atomic level to the microscale level, were employed to elucidate structural origins of enhanced battery performance. This study paves the way for the resource-efficient microstructure design of LiTM cathode materials to maximize capacity and stability via simple adjustment of processing conditions, which is advantageous for mass-production applications.

Hierarchically Structured Core-Shell Design of a Lithium Transition-Metal Oxide Cathode Material for Excellent Electrochemical Performance.

Electron beam damage from transmission electron microscopy of layered lithium transition-metal oxides is a threshold phenomenon that depends on the electron beam energy, which we demonstrate in this study by varying the accelerating voltage of a scanning transmission electron microscope. The electron beam irradiation experiment shows that Ni in LiNiO has much lower threshold energy for displacement than Co in LiCoO, which is supported by DFT calculations predicting that Ni has lower migration energy. The transition-metal ions are reduced from the oxidation state of +3 to +2 during migration from their original positions to the lithium sites, and Ni is more easily reduced than Co because of its electronic configuration. In addition, the high-energy electron beam induces oxygen release, which is another symptom of degradation of materials that occurs more strongly in Ni-containing materials with ion displacement.

In Situ Observation of the Effect of Accelerating Voltage on Electron Beam Damage of Layered Cathode Materials for Lithium-Ion Batteries.

The development of novel anode materials for high energy density is required. Alloying Si with other metals is a promising approach to utilize the high capacity of Si. In this work, we optimized the composition of a Si-Ti-Al ternary alloy to achieve excellent electrochemical performance in terms of capacity, cyclability, and rate capability. The detailed internal structures of the alloys were characterized through their atomic compositions and diffraction patterns. The lithiation process of the alloy was monitored using real-time scanning electron microscopy, revealing that the mechanical stability of the optimized alloy was strongly enhanced compared to that of the pure silicon material.

Sanghun Lee

Department of Biological Sciences

Sungkyunkwan University (SKKU)

Arteriovenous Metabolomics to Measure In Vivo Metabolite Exchange in Brown Adipose Tissue

Sanghun Lee

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Biological Sciences

Sungkyunkwan University (SKKU)

Arteriovenous Metabolomics to Measure In Vivo Metabolite Exchange in Brown Adipose Tissue

Department of Biological Sciences