Changhee Lee

Herein, we applied a novel superconcentrated aqueous electrolyte in calcium-ion batteries for the first time to improve electrochemical performance by decreasing the hydration number and radius of calcium ions. Their charge/discharge capacities with the superconcentrated electrolyte were ca. 13% higher than that with the dilute electrolyte. The cycling performance improved quite remarkably in the superconcentrated electrolyte, because of the suppression of structural collapse of copper hexacyano

This work investigates the electrochemical intercalation of Ca2+ ions into TiS2 in organic electrolytes at room temperature and demonstrates that successful intercalation/de-intercalation can be achieved using a 0.1 M solution of Ca(CF3SO3)2 in propylene carbonate (PC) as an electrolyte. Additionally, further performance (charge/discharge capacity, reversibility, and hysteresis) enhancement is observed when a 0.1 M solution of Ca(CF3SO3)2 in a 1:10 (mol/mol) mixture of PC and dimethyl carbonate

This study investigated the fundamental mechanisms of the loss of capacity of LiNiO₂ (LNO) electrodes for Li⁺ insertion/deinsertion with a special focus on the origin of this deterioration in an aqueous system. <i>In situ</i> Raman spectra revealed that the intercalation of H⁺ ions formed a NiOOH_<i>x</i> film at the surface of LNO during the initial electrochemical cycles; this NiOOH_<i>x</i> film was also confirmed by X-ray photoelectron spe

Herein, mixtures of water and propylene carbonate (PC) containing Ca(CF3SO3)2 were used as electrolytes to improve the electrochemical performance parameters of a Prussian blue analogue electrode, copper hexacyanoferrate, for use in calcium-ion batteries. The performance of the electrode was greatly influenced by the molar ratio of the two solvents (water and PC) in the electrolyte. The electrode exhibited a relatively high capacity when the molar ratio of calcium cations to water in the electro

This study presents the first observation of the electrochemical formation of graphite-F intercalation compounds (GICs) within LiF-containing organic liquid electrolytes. As determined by operando Raman spectroscopy measurements, the peaks corresponding to the G band (i.e., in-plane mode of sp2 bonded carbon with a planar configuration) in highly oriented pyrolytic graphite (HOPG) are separated during the process of electrochemical oxidation, indicating that F-GIC is electrochemically formed in

Abstract Passivation films, the so‐called solid–electrolyte interphase and cathode–electrolyte interphase (CEI), are considered to be essential for the operation of rechargeable batteries because they have a positive impact on electrochemical performance including cyclability. In the field of aqueous Li‐ion batteries (ALIBs) to date, it is generally accepted that these films can only be formed in super‐concentrated electrolytes containing fluorine‐based organic anions such as N(SO 2 CF 3 ) 2 and

This study attempted to stabilize the nanosurface of LiNiO₂ (LNO) electrodes by varying the electrolyte concentration, significantly influencing its initial electrochemical behaviors for use in aqueous lithium-ion batteries. The charge/discharge capacities, reversibility, and cyclability of LNO were improved during initial cycles with an increase in the concentration of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). As determined by the galvanostatic intermittent titration techn

P2-type transition metal layered oxides have attracted attention as high-capacity positive electrode materials for sodium-ion batteries (NIBs). However, due to their Na-deficient compositions, an additional Na+ supplement is necessary for their practical use in NIBs. As we reported recently, the addition of Na2CO3 powder into the P2-type Na2/3[Fe1/2Mn1/2]O2 electrode has proven to be effective in addressing this challenge, as its electrochemical oxidative decomposition compensates for the Na+ de

We investigated the electrochemical behavior and properties of lithium titanate oxide as the negative electrode for calcium ion batteries during charge/discharge tests in tetrahydrofuran (THF)-based electrolyte. The reversible charge and discharge capacities of ~150 and ~145 mAh g –1 were observed, respectively, in THF-based electrolyte. They are larger than those obtained in propylene carbonate-based electrolyte. Moreover, interesting charge/discharge curves were observed, which might be attrib