Publications by authors named "Kyung-Yoon Chung"

In this study, innovative electrode materials for lithium-ion batteries (LIBs) were developed and characterized, demonstrating significant performance enhancements. Initially, NMC622@TiO was synthesized using a wet-chemical method with titanium(IV) ethoxide as the Ti source. Advanced structural investigations confirmed the successful formation of a core@shell structure with negligible cation mixing (Li/Ni) at the NMC622 surface, contributing to enhanced electrochemical performance.

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We reveal the reversible redox mechanism of LiPSCl in composite cathodes for practical all-solid-state lithium-sulfur batteries. The limited electrochemical reactivity of the non-conducting sulfur-based active material induces the formation of LiPSCl decomposition products, which allows the recrystallization of LiPSCl through a reversible redox process, contributing to the composite cathode capacity.

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Metallic Sn (Tin) is a promising anode material for Na-ion batteries owing to its high theoretical capacity of 870 mAh g. However, its large volumetric changes, interfacial instability, and sluggish sodiation kinetics limit its practical applications. Herein, a hierarchical yolk-shell nanohybrid composed of an Sn yolk and a Carbon/Silicon oxycarbide (C/SiOC) bilayer shell is prepared via the simple pyrolysis of a silicone oil dispersion containing an Sn precursor.

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Direct formic acid fuel cells (DFAFCs) stand out for portable electronic devices owing to their ease of handling, abundant fuel availability, and high theoretical open circuit potential. However, the practical application of DFAFCs is hindered by the unsatisfactory performance of electrocatalysts for the sluggish anodic formic acid oxidation reaction (FAOR). Palladium (Pd) based nanomaterials have shown promise for FAOR due to their highly selective reaction mechanism, but maintaining high electrocatalytic durability remains challenging.

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Herein, P2-type layered manganese and ruthenium oxide is synthesized as an outstanding intercalation cathode material for high-energy density Na-ion batteries (NIBs). P2-type sodium deficient transition metal oxide structure, NaMnRuO cathodes where x varied between 0.05 and 0.

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The intrinsic reactivity of lithium (Li) toward ambient air, combined with insufficient cycling stability in conventional electrolytes, hinders the practical adoption of Li metal anodes in rechargeable batteries. Here, a bilayer interphase for Li metal is introduced to address both its susceptibility to corrosion in ambient air and its deterioration during cycling in carbonate electrolytes. Initially, the Li metal anode is coated with a conformal bottom layer of polysiloxane bearing methacrylate, followed by further grafting with poly(vinyl ethylene carbonate) (PVEC) to enhance anti-corrosion capability and electrochemical stability.

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Although sodium-ion batteries (SIBs) offer promising low-cost alternatives to lithium-ion batteries (LIBs), several challenges need to be overcome for their widespread adoption. A primary concern is the optimization of carbon anodes. Graphite, vital to the commercial viability of LIBs, has a limited capacity for sodium ions.

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Application of Si anodes is hindered by severe capacity fading due to pulverization of Si particles during the large volume changes of Si during charge/discharge and repeated formation of the solid-electrolyte interphase. To address these issues, considerable efforts have been devoted to the development of Si composites with conductive carbons (Si/C composites). However, Si/C composites with high C content inevitably show low volumetric capacity because of low electrode density.

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Oxygen evolution reaction (OER) under acidic conditions becomes of significant importance for the practical use of a proton exchange membrane (PEM) water electrolyzer. In particular, maximizing the mass activity of iridium (Ir) is one of the maiden issues. Herein, the authors discover that the Ir-doped calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) perovskite exhibits ultrahigh mass activity up to 1000 A g for the acidic OER, which is 66 times higher than that of the benchmark catalyst, IrO .

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SiO is a promising next-generation anode material for lithium-ion batteries. However, its commercial adoption faces challenges such as low electrical conductivity, large volume expansion during cycling, and low initial Coulombic efficiency. Herein, to overcome these limitations, an eco-friendly in situ methodology for synthesizing carbon-containing mesoporous SiO nanoparticles wrapped in another carbon layers is developed.

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Article Synopsis
  • Developing bulk Bi anodes for Na-ion batteries presents challenges like slow ion diffusion and material fragmentation, but a new strategy successfully overcomes these issues.
  • The bulk Bi transforms into a porous nanostructure during use, which improves sodium ion storage and allows for ultrafast charging and long-lasting performance.
  • The Na-Bi half-cell shows remarkable capacity retention and performance even at extreme charging rates, highlighting the combination of high energy storage, rapid charging capabilities, and durability in battery design.
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Article Synopsis
  • - Metastable phases, which are temporarily stable structures formed under certain conditions, are commonly found in nature and can have better properties than their stable counterparts, making them valuable in materials science.
  • - Crystals often start as metastable phases influenced by factors like temperature and pressure, and they typically transition to more stable forms as they grow over time.
  • - A new approach for discovering metastable materials involves rational design rather than relying on intuition, as demonstrated by the creation of a unique metastable hexagonal close-packed palladium hydride (PdH) through precise control of precursor concentrations.
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Sulfide-based inorganic solid electrolytes have been considered promising candidates for all-solid-state batteries owing to their high ionic conductivity. Compared with oxide-based inorganic solid electrolytes which require high-temperature sintering, the intrinsic deformability of sulfide electrolytes enables the fabrication of all-solid-state batteries by a simple cold pressing method. Nevertheless, the performance of sulfide-based all-solid-state batteries is still unsatisfactory, owing to the insufficient interfacial properties within the composite electrodes.

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We propose a promising electrochemical analysis tool based on the distribution of relaxation times (DRT) to quantify interfacial resistances towards a comprehensive understanding of complex solid-state interfacial phenomena in sulfide-based all-solid-state batteries (ASSBs). Using DRT-assisted impedance analysis, we identify a new resistance component in the range of 10-10 Hz of 3.5 and 0.

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The design of atomically dispersed single atom catalysts (SACs) must consider high metal-atom loading amount, effective confinement, and strong interactions with matrix, which can maximize their catalytic performance. Here reported is a promising method to synthesize SACs on highly conductive multiwall carbon nanotube (MWCNT) supports using pulsed laser confinement (PLC) process in liquid. Atomic cobalt (Co) and phosphorus (P) with a high loading density are homogeneously incorporated on the outer wall of the MWCNT (Co-P SAC MWCNT).

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The development of solid electrolytes (SEs) is a promising pathway to improve the energy density and safety of conventional Li-ion batteries. Several lithium chloride SEs, LiMCl (M = Y, Er, In, and Sc), have gained popularity due to their high ionic conductivity, wide electrochemical window, and good chemical stability. This study systematically investigated 17 LiMCl SEs to identify novel and promising lithium chloride SEs.

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Although several crystalline materials have been developed as Li-ion conductors for use as solid electrolytes in all-solid-state batteries (ASSBs), producing materials with high Li-ion conductivities is time-consuming and cost-intensive. Herein, we introduce a superionic halogen-rich Li-argyrodite (HRLA) and demonstrate its innovative synthesis using ultimate-energy mechanical alloying (UMA) and rapid thermal annealing (RTA). UMA with a 49 G-force milling energy provides a one-pot process that includes mixing, glassification, and crystallization, to produce as-milled HRLA powder that is ∼70% crystallized; subsequent RTA using an infrared lamp increases this crystallinity to ∼82% within 25 min.

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Stretchable energy storage devices are of great interest because of their potential applications in body-friendly, skin-like, wearable devices. However, stretchable batteries are very challenging to fabricate. The electrodes must have a degree of stretchability because the active materials occupy most of the volume, and the separator and packaging should also be stretchable.

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Silicon has a great potential as an alternative to graphite which is currently used commercially as an anode material in lithium-ion batteries (LIBs) because of its exceptional capacity and reasonable working potential. Herein, a low-cost and scalable approach is proposed for the production of high-performance silicon-carbon (Si-C) hybrid composite anodes for high-energy LIBs. The Si-C composite material is synthesized using a scalable microemulsion method by selecting silicon nanoparticles, using low-cost corn starch as a biomass precursor and finally conducting heat treatment under CH gas.

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The structural stability of cathode materials during electrochemical reactions, in particular, under high-rate discharge, is pertinent to the design and development of new electrode materials. This study investigates the structural inhomogeneity that develops within a single LiNi Co Al O (NCA83) particle during a fast discharging process under different cutoff voltages. Some of the NCA83 particles discharged from a high cutoff voltage (4.

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Most active materials for sodium-ion batteries suffer from the problem of low-energy efficiency in the first cycle because of the loss of active sodium ions consumed for the formation of a solid electrolyte interface. To make up for the lost sodium ion, presodiation treatments have been applied, which are effective ways to mitigate the low initial efficiency. Here, we developed a direct-contact method to achieve the presodiation for cathode and anode electrodes and demonstrated the enhanced Coulombic efficiency of the first cycle with improved cyclability and reversible capacity.

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In this study, we synthesize two layered and amorphous structures of germanium phosphide (GeP) and compare their electrochemical performances to better understand the role of layered, crystalline structures and their ability to control large volume expansions. We compare the results obtained with those of previous, conventional viewpoints addressing the effectiveness of amorphous phases in traditional anodes (Si, Ge, and Sn) to hinder electrode pulverization. By means of both comprehensive experimental characterizations and density functional theory calculations, we demonstrate that layered, crystalline GeP in a hybrid structure with multiwalled carbon nanotubes exhibits exceptionally good transport of electrons and electrolyte ions and tolerance to extensive volume changes and provides abundant reaction sites relative to an amorphous structure, resulting in a superior solid-electrolyte interphase layer and unprecedented initial Coulombic efficiencies in both Li-ion and Na-ion batteries.

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Sodium-ion batteries are considered the most promising power source for electrical energy storage systems because of the abundance of sodium and their significant cost advantages. However, high-performance electrode materials are required for their successful application. Herein, we report a monoclinic-type CoMoO material which is synthesized by a simple solution method.

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We determined the interatomic potentials of the Li-[PS] building block in (LiS)(PS) (LPS) and predicted the Li-ion conductivity (σ) of glass-ceramic LPS from molecular dynamics. The Li-ion conduction characteristics in the crystalline/interfacial/glassy structure were decomposed by considering the structural ordering differences. The superior σ of the glassy LPS could be attributed to the fact that ∼40% of its structure consists of the short-ranged cubic S-sublattice instead of the hexagonally close-packed γ-phase.

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The interest in the development of micro-nanostructured metal oxides has been increasing recently because of their advantages as electrode materials in energy storage applications. In this study, dandelion-like ZnxCo3-xO4 microspheres assembled with porous needle-shaped nanosticks were synthesized by co-precipitation followed by a post-annealing treatment. The open space between neighboring nanosticks enables easy infiltration of the electrolyte; therefore, each nanostick is surrounded by the electrolyte solution, which ensures proper utilization of the active material during the electrochemical reaction.

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