<b>Effect of Electrochemical Conditions on Material Removal Rate in Electrochemical Oxidation Assisted Machining</b>

Nam, Eunseok,Lee, Chan-Young,Min, Jaehong,Lee, Sang Jo,Min, Byung-Kwon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.2

<P>Recently, a new process for machining glassy carbon using electrochemical oxidation has been introduced. The process is effective in reducing cracks on the machined surface of glassy carbon, unlike conventional mechanical processes. This paper proposes a method for increasing the electrochemical oxidation rate in this process by applying a high overvoltage to improve the material removal rate. Suitable electrochemical conditions for applying high overvoltage were investigated. Experiments were conducted by varying the electrochemical conditions, including high overvoltage, to compare the material removal rates. The results showed that the material removal rate could be increased by using a high overvoltage. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Investigation of the Electrochemical Behavior of Ytterbium Cations in LiCl-KCl Melt Using Spectro-Electrochemical Methods

Bae, Sang-Eun,Kim, Dae-Hyeon,Lee, Na-Ri,Park, Tae-Hong,Kim, Jong-Yun The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.2

<P>Electrochemical behavior of ytterbium cations in a LiCl-KCl melt was investigated by electrochemical and UV-VIS absorption spectroscopy methods. In the LiCl-KCl melt, ytterbium exists with divalent and trivalent oxidation states. The electrochemical results showed that the electrochemical reactions of the Yb2+/3+ are reversible and controlled by their diffusion rates. UV-VIS absorption spectroscopy results indicate that the Yb2+ and Yb3+ ions in the LiCl-KCl melt have a few strong absorption bands below 400 nm. Additionally, the molar absorptivities of these electronic transitions of Yb2+ and Yb3+ in LiCl-KCl melt are reported. (C) 2015 The Electrochemical Society.</P>

Methodological Consideration on the Prediction of Electrochemical Mechanical Polishing Process Parameters by Monitoring of Electrochemical Characteristics of Copper Surface

Seo, Yong-Jin The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.4

The removal characteristics of copper (Cu) from electrochemical surface by voltage-activated reaction were reviewed to assess the applicability of electrochemical-mechanical polishing (ECMP) process in three types of electrolytes, such as HNO₃, KNO₃ and NaNO₃. Electrochemical surface conditions such as active, passive, transient and trans-passive states were monitored from its current-voltage (I-V) characteristic curves obtained by linear sweep voltammetry (LSV) method. In addition, the oxidation and reduction process of the Cu surface by repetitive input of positive and negative voltages were evaluated from the I-V curve obtained using the cyclic voltammetry (CV) method. Finally, the X-ray diffraction (XRD) patterns and energy dispersive spectroscopy (EDS) analyses were used to observe the structural surface states of a Cu electrode. The electrochemical analyses proposed in this study will help to accurately control the material removal rate (MRR) from the actual ECMP process because they are a good methodology for predicting optimal electrochemical process parameters such as current density, operating voltage, and operating time before performing the ECMP process.

Polymer-Assisted Solution Processing of TiO₂ Thin Films for Resistive-Switching Random Access Memory

Vishwanath, Sujaya Kumar,Jeon, Sanghun,Kim, Jihoon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.2

<P>In this study, we present a polymer-assisted solution (PAS) process to prepare TiO2 electrolyte layers for resistive-switching random access memory (ReRAM). The PAS process utilizes the stability of metal-polymer complexes in the coating solution to form uniform and dense films. In addition, the viscosity of the PAS coating solution can easily be adapted for any currently used coating technique. The electrochemical-metallization-based (ECM-based) ReRAM devices were prepared by spin-coating the PAS coating solution on an indium tin oxide (ITO) glass substrate that is used as the bottom electrode. Cu was deposited on the PAS-TiO2 electrolyte as an electrochemically active metal electrode used as the top electrode. The ECM-based ReRAM with the PAS-TiO2 electrolyte layer demonstrated bipolar resistive-switching behavior with a memory window wider than 13, cycle endurance over 500 cycles, and retention time longer than 10(4) s. Analysis of the conduction mechanism in high and low resistive states indicates that the resistive switching is attributed to the formation and rupture of Cu conducting filaments (CFs) in the PAS-TiO2 electrolyte layer. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Development of High Performance Electrochemical and Physical Biosensors Based on Chemically Modified Graphene Nanostructured Electrodes

Hossain, M. F.,Das, P. S.,Park, J. Y. Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.9

<P>A solvothermal technique with extra treatment was performed to synthesize high quality chemically modified graphene (CG). An environmentally friendly reducing agent, glucose, was used to obtain biocompatible chemically modified graphene. After acidic treatment of glucose treated chemically modified graphene (GCG), contamination free CG sheet was produced. CG suspension was cast on the surface of the plain biosensor surface and nylon filter paper. Pt nanoparticles (PtNP) were deposited on the CG decorated surface by cyclic voltammogram technique. Chitosan - glucose oxidase (chit-GOx) composite and nafion were then integrated by dropped casting technique on the CG/PtNP modified surface. This as-prepared biosensor showed high electrochemical activity for the detection of glucose in phosphate buffered saline (PBS) solution. It exhibited excellent analytical properties including a short response time (4 s), high sensitivity (69.44 mu A/mMcm(-2)), and wide detection range (0.002-12 mM) for glucose sensing. The repeatability, reproducibility, interference phenomena and the stability of the developed sensors were also investigated. The CG based electrode was also evaluated for use as a dry electrode for ECG signal monitoring. The performance of the dry electrode was excellent in comparison to the conventional wet electrodes. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Effects of Zr⁴⁺ Doping on the Electrochemical Characteristics of Li₂FeP₂O₇/C in Lithium Ion Batteries

Ryu, Da-Jeong,Lee, Seong-Hun,Ryu, Kwang-Sun Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.13

<P>Using splash combustion synthesis, Zr4+-doped Li2Fe1-xZrx/2P2O7/C (x = 0, 0.01, 0.02, 0.03, and 0.04) composites were successfully synthesized in order to increase the redox voltage and c-rate performance. X-ray diffraction (XRD) patterns indicated that the successfully obtained Li2Fe1-xZrx/2P2O7/C had a monoclinic structure. The results indicated that the zirconium atoms within the Zr4+-doped system do not change the lattice structure of Li2FeP2O7, but do enlarge the lattice volume. During the de-intercalation and intercalation of lithium ions, the doped zirconium atoms protect the Li2FeP2O7 structure from spontaneous structural rearrangement, which can lower the reaction potential. Among the various samples, Li2Fe0.97Zr0.015P2O7/C exhibited excellent rate and cycling performance. We investigated the electrochemical performance and lithium ionic diffusion coefficient by using three electrochemical perturbation methods: cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), and potentiostatic intermittent titration technique (PITT). Li2Fe0.97Zr0.015P2O7/C exhibited relatively good electrochemical performance in comparison with Li2FeP2O7/C. We further investigated the lithium ion diffusion behavior by using CV, GITT, and PITT. Li2Fe0.97Zr0.015P2O7/C demonstrated more rapid ionic diffusion than Li2FeP2O7/C did due to its higher diffusion coefficient value. Therefore, these ionic kinetic studies were helpful to understand the enhanced electrochemical performance. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Electrochemical Lithium Recycling System toward Renewable and Sustainable Energy Technologies

Bae, Hyuntae,Hwang, Soo Min,Seo, Inseok,Kim, Youngsik The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.7

<P>A new system of lithium recycling is designed to recover Li from materials containing waste Li. This waste-to-lithium (WTL) system operates based on electrochemical reaction at room temperature using three functional sections: two cathode compartments, one for the waste materials and one for recycling the recovered Li, and one Li-harvesting anode compartment located between the two cathode compartments. By charging the system, Li ions from waste Li-containing materials are extracted and converted into Li metal in the harvesting anode compartment. The harvested Li metal can be transformed via electrochemical reactions with water into useful Li precursors such as LiOH and Li2CO3, which are commonly used Li source chemicals. The concept of the WTL system is proved using well-known cathode materials from Li ion batteries and a commercial Li ion battery pack as the waste Li-containing materials. The harvested Li metal shows a purity of similar to 99%, and the produced Li2CO3 is phase-pure without any notable secondary phase. Compared to existing Li recycling technologies, which are generally complicated, time-consuming chemical and heating processes, the WTL system is straightforward and can be operated at room temperature without using any deleterious acid chemicals, thus opening a new avenue for cost-effective, eco-friendly Li-recycling systems. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Tailored Metal Oxide Thin Film on Polyethylene Separators for Sodium-Ion Batteries

Kim, Jin Il,Heo, Jinwoo,Park, Jong Hyeok Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.9

<P>The development of polymer separators for Na+-ion batteries has not been of interest because conventional polyolefin (e.g., polyethylene or polypropylene) separators are not suitable for the solvation of Na+-ion-containing electrolytes. Here, we report a simple surface modification method based on chemical vapor deposition of SiO2 applied to a polyethylene separator for Na+-ion batteries. A thin SiO2 layer is coated uniformly onto a porous polymer separator with the negligibly increased total separator thickness. Improved wetting ability of the SiO2-film-coated polyethylene separators with a polar electrolyte based on ethylene carbonate (EC) and dimethyl carbonate (DMC) solvents is demonstrated, with superior electrochemical performance characteristics, such as initial specific capacity, C-rate and cyclic stability. In addition, the thin SiO2 coating film results in substantially suppressed thermal shrinkage, which may lead to improvements in the thermal and dimensional stability of Na+-ion batteries. Compared to a glass-fiber separator and the conventional PE separator, the metal-oxide-thin-film-coated polyethylene separator will accelerate the development of Na+-ion batteries for various electrochemical energy storage applications. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Enhanced Electrocatalytic Activity of Cu₂S-Polyaniline Heterostructure Counter Electrode for Quantum Dot-Sensitized Solar Cells

Vijayakumar, Elayappan,Quy, Vu Hong Vinh,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12

<P>The Cu2S-Polyaniline (Cu-P) counter electrode (CE) was prepared by electropolymerization of polyaniline (PANI) on a FTO/Cu2S film. The surface morphology and crystallinity of the counter electrode were examined. The FTO/Cu-P CE provided significantly enhanced electrochemical activity and a faster charge transfer rate compared to the platinum (Pt), Cu2S, PANI, and PANI-Cu2S (P-Cu) CEs because of the synergistic effect between the high carrier mobility of PANI and the good electrocatalytic activity of Cu2S on the polysulfide electrolyte. Besides, the FTO/Cu-P CE exhibited excellent electrochemical stability, due to the strong interaction between the metal particles and electronegative nitrogen of PANI. The quantum dot-sensitized solar cell (QDSSC) with the FTO/Cu-P heterostructure CE exhibited a higher energy conversion efficiency (4.12%) than those with Pt (1.85%), Cu2S (3.71%), PANI (0.77%), and PANI-Cu2S (P-Cu) (1.01%) CEs. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Tris(pentafluorophenyl)silane as a Solid Electrolyte Interphase (SEI)-Forming Agent for Graphite Electrodes

Lee, Tae Jin,Lee, Jeong Beom,Yoon, Taeho,Park, Hosang,Jurng, Sunhyung,Kim, Daesoo,Jung, Jiwon,Soon, Jiyong,Ryu, Ji Heon,Lee, Kyu Tae,Oh, Seung M. The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.9

<P>Tris(pentafluorophenyl) silane (TPFPS) is examined as a solid electrolyte interphase (SEI)-forming agent for a graphite electrode. The surface film (SEI layer) generated from a conventional carbonate-based electrolyte (TPFPS-free) is so poorly passivating that continued reductive electrolyte decomposition and concomitant film deposition are employed to increase its thickness. Thus, the electrode develops more sluggish kinetics. An electrochemical quartz crystal microbalance (EQCM) study demonstrates that TPFPS is preferentially electroreduced before the organic carbonate solvents on the copper electrode, as predicted from ab initio calculations. Preferential electroreduction of TPFPS over the carbonate-based electrolyte is also observed after first lithiation of the graphite electrode. This gives a more compact and evenly covered SEI layer. The passivating ability of the resulting SEI layer is so high that additional electrolyte decomposition/film deposition is greatly suppressed. Consequently, both Li/graphite half-cell and graphite/LiCoO2 full-cell show higher Coulombic efficiency and better capacity retention in the TPFPS-added electrolyte. (C) 2017 The Electrochemical Society. All rights reserved.</P>