Dong Wook Kim

Chlorine- and vinyl-functional PDMS, readily synthesized via copolymerization, forms a homogeneous solution in hydrophilic acrylate monomers, enabling the fabrication of high-permittivity photocured elastomer films.

Amorphous materials have garnered significant research interest because of their high structural tolerances and useful functionalities. Here, we develop an effective synthesis method for atomically thin, highly disordered RuO₂ nanosheets that exhibit a promising electrocatalytic performance and a distinct pH-dependent operation mechanism. The poor orbital overlap and coordinatively unsaturated nature of the Ru ions in the highly disordered RuO₂ nanosheets have a synergistic effect on the electrocatalytic performance by enhancing surface adsorption and the activation of lattice oxygen. The highly disordered RuO₂ nanosheets exhibit high electrocatalytic activities in the oxygen evolution reactions (OERs) performed in both alkaline and acidic electrolytes. Various in situ spectroscopic investigations reveal that structural disordering causes a greater contribution of the lattice oxygen participation mechanism in acidic media than in alkaline media. This pH-dependent mechanism can be attributed to the amorphization-induced enhancement of lattice oxygen occupation in the acidic OER medium and increased hydroxide adsorption in the alkaline OER medium. Such disorder-driven pH tuning of the electrocatalytic operation mechanism enables the fabrication of pH-universal high-performance electrocatalysts.

All-solid-state Li-metal batteries (ASSLBs) are promising for next-generation energy storage systems owing to their high energy density and intrinsic safety. However, their practical applications are impeded by challenges such as low ionic conductivity, uncontrolled Li-dendrite growth, and interfacial instability. This study presents a scalable strategy to address these limitations by incorporating ferroelectric BaTiO₃ into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanowebs. The 3D nanowebs were utilized to prepare composite solid polymer electrolytes (3DCSPEs), which exhibited significantly higher ionic conductivity (8.5 × 10^-4 S cm^-1 at 25 °C) and a higher Li-ion transference number (0.78) than a PVDF-HFP-based solid polymer electrolyte (PSPE). The 3DCSPEs effectively regulated Li-ion flux, suppressed dendrite growth, and stabilized interfacial contact. In battery tests, LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811)/3DCSPE/Li cells outperformed conventional NCM811/PSPE/Li cells, exhibiting a higher capacity (143.72 mA h g^-1 at 0.1 C) and superior prolonged cycle stability over 600 cycles at 0.2 C at 25 °C. Additionally, 3DCSPE mitigated cathode cracking and enhanced ion transport, demonstrating its potential to advance Li polymer battery technology. This study clarifies the pivotal role of in situ cross-linked ferroelectric 3D nanowebs as a novel approach for addressing the key challenges in ASSLBs, facilitating the development of advanced Li polymer batteries.

In the quest to enhance the safety of lithium-ion batteries, substantial research is underway to develop all-solid-state batteries, facing challenges in achieving high ion conductivity in solid electrolytes. This study aims to enhance the ion conductivity by incorporating carbon-doped graphitic carbon nitride (C-doped g-C₃N₄) microspheres as an inorganic filler into the poly(ethylene oxide)-based solid polymer electrolyte (SPE). Leveraging the advantageous properties of g-C₃N₄ as an effective inorganic filler by enhancing its Lewis acid-base interactions with lithium, we modified g-C₃N₄ through carbon doping to improve the ionic conductivity of the SPE. Our experimental analysis supports the increased lithium transference number after hybridizing electrolytes with C-doped g-C₃N₄, signifying heightened ion mobility resulting from carbon substitution on g-C₃N₄. Subsequent density functional theory (DFT) calculations reveal increased lithium binding energy due to the carbon doping of g-C₃N₄, thereby ultimately enhancing the ion conductivity by promoting salt dissociation. Optimizing carbon doping levels and hybrid electrolyte composition yields improved ion conductivity and electrochemical performance, with optimal outcomes observed at 7% C-doped g-C₃N₄ with SPE. Evaluation in a pouch cell with the NCM811 cathode underscores the applicability of the hybrid electrolyte on a large scale, showcasing promising advancements in battery technology. Our carbon-doped g-C₃N₄ filler demonstrates promising potential in advancing ion conductivity through enhanced salt dissociations.

Solid polymer electrolytes have garnered significant attention for lithium batteries because of their flexibility and safety. However, poor ionic conductivity, lithium dendrite formation, and high impedance hinder their practical application. In this study, a thin, flexible, 3D hybrid solid electrolyte (3DHSE) is prepared by in situ thermal cross‐linking polymerization with electrospun 3D nanowebs. The 3DHSE comprises Al‐doped Li₇La₃Zr₂O₁₂ (ALLZO) embedded in electrospun poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) nonwoven 3D nanowebs and an in situ cross‐linked polyethylene oxide (PEO)‐based solid polymer electrolyte. The 3DHSE exhibits high tensile strength (6.55 MPa), a strain of 40.28%, enhanced ionic conductivity (7.86 × 10⁻⁴ S cm⁻¹), and a superior lithium‐ion transference number (0.76) to that of the PVDF‐HFP‐based solid polymer electrolyte (PSPE). This enables highly stable lithium plating/stripping cycling for over 900 h at 25 °C with a current density of 0.2 mA cm⁻². The LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811)/3DHSE/Li cell has a higher capacity (140.56 mAh g⁻¹ at 0.1 C) than the NCM811/PSPE/Li cell (124.88 mAh g⁻¹ at 0.1 C) at 25 °C. The 3DHSE enhances mechanical properties, stabilizes interfacial contact, improves ion transport, prevents NCM811 cracking, and significantly boosts cycling performance. This study highlights the potential of the 3DHSE as a candidate for advanced lithium polymer battery technology.

Sulfide‐based inorganic solid electrolytes are promising materials for high‐performance safe solid‐state batteries. The high ion conductivity, mechanical characteristics, and good processability of sulfide‐based inorganic solid electrolytes are desirable properties for realizing high‐performance safe solid‐state batteries by replacing conventional liquid electrolytes. However, the low chemical and electrochemical stability of sulfide‐based inorganic solid electrolytes hinder the commercialization of sulfide‐based safe solid‐state batteries. Particularly, the instability of sulfide‐based inorganic solid electrolytes is intensified in the cathode, comprising various materials. In this study, carbonate‐based ionic conductive polymers are introduced to the cathode to protect cathode materials and suppress the reactivity of sulfide electrolytes. Several instruments, including electrochemical spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy, confirm the chemical and electrochemical stability of the polymer electrolytes in contact with sulfide‐based inorganic solid electrolytes. Sulfide‐based solid‐state cells show stable electrochemical performance over 100 cycles when the ionic conductive polymers were applied to the cathode.