Jung-Ki Park

Mussel‐Inspired Polydopamine‐Treated Polyethylene Separators for High‐Power Li‐Ion Batteries

Due to high energy densities and excellent cycle lives, Li-ion batteries (LIBs) have rapidly spread into portable electronics applications. [ 1–3 ] However, their performance standards in various areas including energy and power densities, cycle lives, and safety concerns need to be improved further for the future emerging markets, particularly targeting sustainable road transportation represented by electric vehicles (EVs). [ 1 , 3–5 ] Among the various standards, the low power density should be urgently addressed to enable the emergence of those applications. [ 4 , 6 , 7 ]

Mussel‐Inspired Adhesive Binders for High‐Performance Silicon Nanoparticle Anodes in Lithium‐Ion Batteries

Conjugation of mussel-inspired catechol groups to various polymer backbones results in materials suitable as silicon anode binders. The unique wetness-resistant adhesion provided by the catechol groups allows the silicon nanoparticle electrodes to maintain their structure throughout the repeated volume expansion and shrinkage during lithiation cycling, thus facilitating substantially improved specific capacities and cycle lives of lithium-ion batteries.

Ionic conduction in plasticized PVC/PMMA blend polymer electrolytes

The new plasticized polymer electrolyte composed of the blend of poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) as a host polymer, the mixture of ethylene carbonate and propylene carbonate as a plasticizer, and LiCF3SO3 as a salt was studied. The effect of the PMMAPVC blend ratio and the plasticizer content on the ionic conductions in these electrolytes were investigated. The electrolyte films revealed a phase separated morphology due to immiscibility of the PVC with the plasticizer; the PVC-rich phase and the plasticizer-rich phase were produced during the film casting. The mechanical property was significantly enhanced by the incorporation of PVC into the electrolyte system. The ionic conductivity decreased with increasing the PVCPMMA ratio and increased with increasing the plasticizer content. These behaviors were explained in terms of the morphology of the film. Since the plasticizer-rich phase contains much more plasticizer than the PVC-rich phase, the ions preferentially move through plasticizer-rich phase. Due to the slow ionic transport through the PVC-rich phase, the conductivity decreased with increasing PVCPMMA ratio.

Directional Photofluidization Lithography: Micro/Nanostructural Evolution by Photofluidic Motions of Azobenzene Materials

This review demonstrates directional photofluidization lithography (DPL), which makes it possible to fabricate a generic and sophisticated micro/nanoarchitecture that would be difficult or impossible to attain with other methods. In particular, DPL differs from many of the existing micro/nanofabrication methods in that the post-treatment (i.e., photofluidization), after the preliminary fabrication process of the original micro/nanostructures, plays a pivotal role in the various micro/nanostructural evolutions including the deterministic reshaping of architectures, the reduction of structural roughness, and the dramatic enhancement of pattern resolution. Also, DPL techniques are directly compatible with a parallel and scalable micro/nanofabrication. Thus, DPL with such extraordinary advantages in micro/nanofabrication could provide compelling opportunities for basic micro/nanoscale science as well as for general technology applications.

SEI Layer Formation on Amorphous Si Thin Electrode during Precycling

The morphological and compositional changes of the solid electrolyte interphase (SEI) layer formed on the surface of Si thin electrodes during precycling were investigated. At the beginning of charging, the native layer (SiO 2 and silanol) covering the surface of the Si thin electrode is readily destroyed and a new SEI layer is formed by the decomposition of both organic solvents and anions. At this stage, the interfacial resistance decreases to a minimum level. Thereafter, the interfacial resistance increases with charging due to the growth of an SEI layer, which is mainly originated from the decomposition of organic solvents. During the discharging process, an SEI layer was formed mainly by the decomposition of anions.

Sodium zinc hexacyanoferrate with a well-defined open framework as a positive electrode for sodium ion batteries

A modified Prussian blue analogue, Na(2)Zn(3)[Fe(CN)(6)](2)·xH(2)O, was investigated as a positive electrode material. Utilizing a well-defined channel structure, the compound exhibits a clear electrochemical activity at around 3.5 V vs. Na/Na(+) with a reversible capacity of 56.4 mA h g(-1) and good cycle life.

Effect of silica on the electrochemical characteristics of the plasticized polymer electrolytes based on the P(AN-co-MMA) copolymer

Abstract Composite polymer electrolyte films consisting of poly(acrylonitrile-co-methyl methacrylate) (P(AN-co-MMA)), EC–PC, LiClO 4 salts, and also silica particles have been prepared, and their electrochemical properties were studied. A maximum in the ion conductivity was found for the plasticized polymer electrolyte containing 10 wt% silica with EC–PC and was 1.7×10 −4 S/cm at −15°C and 1.9×10 −3 S/cm at 25°C. The reduction in T g of the plasticizer-rich phase in the composite polymer electrolytes due to the interaction between the added silica and lithium cation seems to be a main reason for the initial increase of the ion conductivities with the increase in the silica content. The decrease in the ion conductivity with the silica content at the higher silica content is expected to be attributed to the increase of viscosity of the plasticizer-rich phase and the decrease in the charge carrier numbers. The stability of interfacial resistance between the composite polymer electrolyte and the lithium electrode was found to be enhanced with increase of the silica content in the range studied.

Sustainable Redox Mediation for Lithium–Oxygen Batteries by a Composite Protective Layer on the Lithium‐Metal Anode

A synergic combination of a soluble -redox mediator and a protected Li metal -electrode to prevent the self-discharge of the redox mediator is realized by -exploiting a 2,2,6,6-tetramethylpiperidinyl 1-oxyl (TEMPO) redox mediator and an Al2 O3 /PVdF-HFP composite -protective layer (CPL). Stabilization of Li metal by simple CPL coating is effective at -suppressing the chemical reduction of the oxidized TEMPO and opens up the possibility of sustainable redox mediation for robust cycling of Li-O2 batteries.

New polymer electrolytes based on PVC/PMMA blend for plastic lithium-ion batteries

Abstract The electrochemical properties of the polymer electrolytes based on poly(vinyl chloride)/poly(methyl methacrylate) blend with micro-pore structure have been investigated. The introduction of poly(methyl methacrylate) (PMMA) into the poly(vinyl chloride) (PVC) matrix enhanced compatibility between the polymer matrix and the liquid electrolyte (EC/DMC/LiClO4). The addition of silica into the polymer blend generated a micro-pore structure in the polymer matrix and increased the uptake amount of the liquid electrolyte. The ion conductivity of the polymer electrolyte was increased with the increase in the PMMA content in the blend and the room temperature ion conductivity of the polymer electrolyte based on PVC/PMMA (5:5, w/w) blend was 1.1×10−3 S/cm. The charge–discharge behavior of the unit cell was also investigated.

Effect of P(lLa-co-εCL) on the compatibility and crystallization behavior of PCL/PLLA blends

This article describes the compatibility of two semicrystalline polymers, poly(e-caprolactone) (PCL) and poly(l-lactic acid) (PLLA). The compatibility of the PCL/PLLA blends was enhanced by the compatibilizing effect of the poly(l,l-lactide-co-e-caprolactone) [P(lLA-co-eCL)]. A discussion details the effect of the concentration of the compatibilizing agent, the copolymer of l,l-lactide and e-caprolactone of a 50/50 mol ratio [P(lLA-co-eCL)], on the compatibility and the crystallization behavior of the blends of PCL and PLLA. It was found that the addition of P(lLA-co-eCL) could suppress the crystallization of PLLA at its Tc and induced the concurrent crystallization of PLLA and PCL.