• Journal of Electrochemical Science and Technology
• /
• 제5권4호
• /
• pp.95-104
• /
• 2014

Electrochemical performance of Li-ion cells with $LiMn_2O_4$ cathodes and graphite anodes with carbonates electrolytes containing quaternary ammonium-based room temperature ionic liquids (ILs) is investigated. Eight different ILs based on tetraalkylammonium, pyrrolidinium or piperidinium cations paired with bis(trifluoromethylsulfonyl)imide or tris(pentafluoroethyl)trifluorophosphate anions are examined in combination with dimethyl carbonate as a main solvent and fluoroethylene carbonate as a solid electrolyte interface forming agent. It is shown that cycling properties of the cells are strongly affected by the content of ILs in the electrolyte mixtures and its increase corresponds to lower discharge capacity retention. Since viscosity and conductivity of ILs are of a great importance for the electrolytes formulation, some kind of combined parameter should be used for the assessment of IL applicability and calculated values of Walden products for neat ILs represent one of the possible options. Besides, positive effect of ILs on reduction of flammability and enhancement of thermal stability of electrolytes in contact with charged electrodes have been demonstrated by means of self-extinguishing time test and differential scanning calorimetry respectively.

• 한국재료학회지
• /
• 제27권3호
• /
• pp.161-165
• /
• 2017

In this paper, synthesis of terephthalate intercalated Zn-Al: Layered double hydroxides (LDHs) was studied. We designed freestanding Zn-Al: carbonate LDH nanosheets for a facile exchange technique. The as-prepared Zn-Al carbonate LDHs were converted to terephthalate intercalated Zn-Al:LDHs by ion exchange method. Initially, Al-doped ZnO (AZO) thin films were deposited on p-Si (001) by facing target sputtering. For synthesis of free standing carbonate Zn-Al:LDH, we dipped the AZO thin film in naturally carbonated water for 3 hours. Further, Zn-Al: carbonate LDH nanosheets were immersed in terepthalic acid (TA) solution. The ion exchange phenomena in the terephthalate assisted Zn-Al:LDH were confirmed using FT-IR analysis. The crystal structure of terephthalate intercalated Zn-Al:LDH was investigated by XRD pattern analysis with different mole concentrations of TA solution and reaction times. The optimal conditions for intercalation of terephthalate from carbonated Zn-Al LDH were established using 0.3 M aqueous solution of TA for 24 hours.

• 대한화학회지
• /
• 제32권4호
• /
• pp.351-357
• /
• 1988

Propanediol-1,2-carbonate (PDC) 용매중에서 우라닐 화합물의 전기화학적 환원반응 메카니즘을 전압전류법으로 조사하여 봉우리 전위의 위치, 한계전류의 성질, 한계전류와 온도 및 농도의 관계, 전극반응의 가역성, 양성자 공여체인 페놀의 첨가에 대한 영향등을 기술하였다. 또 우라닐 화합물의 수용액에 PDC의 양을 점차 증가시킨 혼합용매에서의 전극반응도 조사하였다. 우라닐 화합물의 비가역적 전극반응에 관여하는 전이계수 및 속도상수등의 반응 속도론적 파라미터를 Koutecky의 이론에 따라 결정하였으며, ${\Delta}H,\;{\Delta}G\;및\;{\Delta}S$등에 열역할적 파라미터도 계산하였다.

• 대한화학회지
• /
• 제48권3호
• /
• pp.266-272
• /
• 2004

소형 고체상 전극에 단일 조성 실온 경화형(one-component room temperature vulcanizing type) 실리콘러버 730(730 RTV)을 지지체로 도입하여 가소제가 필요 없는 탄산이온선택성 전극막을 개발하였다. 본 연구에서 최적화된 탄산이온선택성 전극막의 조성은 85.75 wt%의 730 RTV, 11.08 wt%의 trifluoroacetyl-p-decylbenzene(TFADB), 3.17 wt%의 tridodecyl-methylammonium chloride(TDMACl)로 제조 되었고, 우수한 전기화학적 특성(감응기울기 (26.3 mV/dec.), 선택성($logKT^{pot}_{CO_{2},Cl^-}$= -4.00, $logKT^{pot}_{TCO_{2},Sal^-}$=1.69), 검출한계(4.0${\times}10^{-4}M$))을 보였으며, 이와 같은 조성의 막을 도입한 평면형 고체상 센서는 60일 이상 초기특성을 유지하였다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.553-556
• /
• 2006

Generally, concrete is one of the most widely used construction materials, because of its good durability to cost ratio. However, when subjected to severe environments its durability can significantly decline due to various harmful conditions. In this article, we would like to investigate a chloride ion diffusion of cement matrix with inert filler, which ground calcium carbonate(GCC). For the experimental results of the chloride ion diffusion, as the addition of GCC makes decreasing the permeability by micro-filler effect, the matrix of 5-15% ratio of replacement are superior to the GCC0 mortar matrix with respect to durability of cement matrix in this scope.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2017년도 춘계학술대회 논문집
• /
• pp.169-169
• /
• 2017

Due to key roles for the electrochemical stability and charge capacity the solid-electrolyte interphase (SEI) has been extensively studied in anodes of a Li-ion battery cell. There is, however, few of investigation for cathodes. Using first-principles based calculations we describe atomic-level process of the SEI layer formation at the interface of a carbonate electrolyte and $LiMn_2O_4$ spinel cathode. Furthermore, using beyond the conventional density functional theory (DFT+U) calculations we examine the work function of the cathode and frontier orbitals of the electrolyte. Based on the results we propose that proton transfer at the interface is an essential mechanism initiating the SEI layer formation in the $LiMn_2O_4$. Our results can guide a design concept for stable and high capacity Li-ion battery cell through screening an optimum electrolyte fine-tuned energy band alignment for a given cathode.

• 한국지반공학회논문집
• /
• 제28권3호
• /
• pp.67-75
• /
• 2012

본 연구에서는 식물추출액을 이용하여 모래 입자 사이에 친환경적으로 탄산칼슘을 석출시켜 모래 고결을 유발하고자 하였다. 식물추출액에는 고결유발 미생물(예: $Sporosarcina$ $pasteurii$)과 같이 요소를 탄산이온과 암모늄이온으로 분해하는 우레아제 성분이 포함되어 있다. 분해된 탄산이온과 용액 속에 녹아 있는 칼슘이온이 결합하여 탄산칼슘을 석출시키는 원리를 이용하여 모래의 고결을 유도하였다. 깨끗한 낙동강모래에 식물추출액과 요소 그리고 칼슘원(염화칼슘 또는 수산화칼슘)을 혼합한 용액을 섞어서 비빈 다음 다짐방법으로 공시체를 제작하였다. 요소의 농도를 세 종류로 달리하였으며, 제작된 공시체를 실내($18^{\circ}C$)에서 3일 동안 양생시킨 다음 일축압축시험과 SEM 및 XRD분석을 실시하여 사질토의 고결 정도를 연구하였다. 칼슘원에 관계없이 요소의 농도가 높을수록 탄산칼슘이 더 많이 침전되어 일축압축강도는 식물추출액을 사용하지 않은 경우보다 최대 10배까지 증가하는 경향을 보였다. 염화칼슘을 사용한 공시체가 수산화칼슘을 사용한 경우보다 더 높은 강도를 나타내었다.

• Bulletin of the Korean Chemical Society
• /
• 제32권1호
• /
• pp.105-108
• /
• 2011

The cycling behavior of $Li_4Ti_5O_{12}$ electrode in the ionic liquid (IL)-based electrolytes containing 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide and a small amount of additive (vinylene carbonate, ethylene carbonate, fluoroethylene carbonate) was investigated. The $Li_4Ti_5O_{12}$ electrode in the IL electrolyte with an additive exhibited reversible cycling behavior with good capacity retention. Electrochemical impedance spectroscopy and FTIR studies revealed that an electrochemically stable solid electrolyte interphase was formed on the $Li_4Ti_5O_{12}$ electrode in the presence of vinylene carbonate and ethylene carbonate during cycling.

• 한국산업융합학회 논문집
• /
• 제25권6_3호
• /
• pp.1275-1284
• /
• 2022

This study provides an investigating the electrolyte reaction characteristics during thermal runaway of a lithium-ion battery(LIB). Dimethyl carbonate(DMC) is known as the main substance that makes up the electrolyte. The mono-molecular decomposition characteristics of DMC were derived through numerical analysis. Cobalt oxide can release oxygen under high temperature conditions. Also, DMC is converted to CH₄, H₂, CO, and CO₂. Especially, it was found that the decomposition of the DMC begins at a temperature range of 340-350℃, which dramatically increases the internal pressure of the LIB. In the by-products gases, the molar ratio of CO and CO₂ changed according to the molecular structure of DMC and temperature conditions. The correlation of the [CO]/[CO₂] ratio according to the temperature during thermal runaway was derived, and the characteristics of the reaction temperature could be estimated using the molar ratio as an indicator. In addition, the oxidation and decomposition characteristics of DMC according to the residence time for each temperature were estimated. When DMC is exposed to low temperature for a long time, both oxidation and decomposition may occur. There is possibility of not only increasing the internal pressure of the LIB, but also promoting thermal runaway. In this study, internal environment of LIB was identified and the reaction characteristics between the active materials of the cathode and electrolyte were investigated.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2017년도 춘계학술대회 논문집
• /
• pp.150.2-150.2
• /
• 2017

This research was conducted to investigate in detail the effect of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions on the electrochemical properties of the thin air-formed oxide film-covered AZ31 Mg alloy. In this work, native air-formed oxide films on AZ31 Mg alloy samples were prepared by knife-abrading method and the changes in the electrochemical properties of the air-formed oxide film were investigated in electrolytes containing 0.01 M, 0.05 M and 0.1 M of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions. It was observed that the trend of open circuit potential (OCP) transients changed only in the solution containing $PO_4{^{3-}}$ ions. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) showed that the resistance of the new surface films formed in fluoride ion containing bath increased with the increase in concentration of fluoride ions but the resistance of surface films formed in carbonate ion containing bath decreased with the increase in concentration of carbonate ions. The potentiodynamic polarization curves illustrated that under anodic polarization, there was growth of porous passive layer only in fluoride ion containing solution while the surface layer formed in phosphate and carbonate ion containing solutions lost its passivity at high anodic potential of $2.5V_{Ag/AgCl}$.