Jun-Yeong Mun

An organic redox flow battery adopting tris(2,2'-bipyridine)nickel(II)tetrafluoroborate (Ni(Bpy)3(BF4)2) and tris(2,2'-bipyridine)iron(II)tetrafluoroborate (Fe(BPy)3(BF4)2)) in propylenecarbonate electrolyte is investigated. With cyclic voltammetry, the redox current of one-electron related Fe(II)/Fe(III) and two-electron related Ni(II)/Ni(0) appears at 0.65 V and −1.66 V (vs. Ag/Ag+), respectively and their cycleabilities are highly stable during 100 cycles. Their charge-discharge characteristi

Silicon is greatly promising for high-capacity anode materials in lithium-ion batteries (LIBs) due to their exceptionally high theoretical capacity. However, it has a big challenge of severe volume changes during charge and discharge, resulting in substantial deterioration of the electrode and restricting its practical application. This conflict requires a novel binder system enabling reliable cyclability to hold silicon particles without severe disintegration of the electrode. Here, a physicall

The LiFePO 4 surface is coated with AlF 3 via a simple chemical precipitation for aqueous rechargeable lithium ion batteries (ARLBs). During electrochemical cycling, the unfavorable side reactions between LiFePO 4 and the aqueous electrolyte (1 M Li 2 SO 4 in water) leave a highly resistant passivation film, which causes a deterioration in the electrochemical performance. The coated LiFePO 4 by 1 wt % AlF 3 has a high discharge capacity of 132 mAh g –1 and a highly improved cycle life, which sho

Low-temperature performance of the rechargeable batteries is limited because of a narrow temperature range of the electrolyte. Despite the aqueous electrolyte having a lower freezing point than the ethelyenecarbonate for conventional lithium-ion batteries, its freezing point is as high as 0 °C. Antifreeze additive of ethylene glycol for aqueous electrolyte solutions is used to improve the low-temperature performance of aqueous rechargeable lithium-ion batteries. The suitable contents of ethylene

Although sodium ion batteries (NIBs) have gained wide interest, their poor energy density poses a serious challenge for their practical applications. Therefore, high-energy-density cathode materials are required for NIBs to enable the utilization of a large amount of reversible Na ions. This study presents a P2-type Na 0.67 Co 1– x Ti x O 2 ( x < 0.2) cathode with an extended potential range higher than 4.4 V to present a high specific capacity of 166 mAh g –1 . A group of P2-type cathodes conta

For high rate capability and energy density of lithium ion batteries, over-lithiated layered cathodes coated by multiwall carbon nanotube were prepared by a novel dry method without decay in the structure.

A bismuth oxide electrode, delivering high capacity, as an anode material for sodium-ion batteries was simply prepared. The electrochemical properties of bismuth oxide were studied by operando X-ray absorption near edge structure spectroscopy and ex situ X-ray diffraction methods. A bismuth oxide/carbon composite showed enhanced cycle stability at high current densities.

Abstract The chemical composition significantly affects the inherent electrical surface properties of the graphite and SiO electrodes, which further, significantly alters the thermal stability of solid electrolyte interphase (SEI) on the negative electrodes. Because the work function of the graphite edge plane is lower than that of the SiO 2 ‐dominant SiO electrode when the electrode is initially lithiated, charge transfer toward the electrolyte is hindered by the high work function of SiO 2 . G

Abstract A breakthrough utilizing an anionic redox reaction (O 2− /O n− ) for charge compensation has led to the development of high‐energy cathode materials in sodium‐ion batteries. However, its reaction results in a large voltage hysteresis due to the structural degradation arising from an oxygen loss. Herein, an interesting P2‐type Mn‐based compound exhibits a distinct two‐phase behavior preserving a high‐potential anionic redox (≈4.2 V vs Na + /Na) even during the subsequent cycling. Through

A comparative study is made on the surface film formation on the high-voltage LiNi0.5Mn1.5O4 positive electrode at elevated temperature (55°C) in two different electrolytes; LiPF6/organic carbonate and LiTFSI/ionic liquid (propylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide, PMPyr-TFSI). The surface film derived by a decomposition of the former electrolyte is enriched by inorganic fluorinated species, which becomes thicker with cycling to lead a continued electrode polarization and cell