음이온 교환막의 정확한 OH^-전도도 및 CO₂ 피독 효과 분석을 위한 전기화학적 측정법

김수연,권후근,이혜진,정남기,배병찬,신동원,Kim, Suyeon,Kwon, Hugeun,Lee, Hyejin,Jung, Namgee,Bae, Byungchan,Shin, Dongwon 한국전기화학회 2022 한국전기화학회지 Vol.25 No.2

The anion exchange membrane used in alkaline membrane fuel cells transports hydroxide ions, and ion conductivity affects fuel cell performance. Thus, the measurement of absolute hydroxide ion conductivity is essential. However, it is challenging to accurately measure hydroxide ion conductivity since hydroxide ions are easily poisoned in the form of bicarbonate by carbon dioxide in the atmosphere. In this study, we applied electrochemical ion exchange treatment to measure the absolute hydroxide ion conductivity of the anion exchange membrane. In addition, we investigated the effect of carbon dioxide poisoning of hydroxide ions on electrochemical performance by measuring bicarbonate conductivity. Commercial anion exchange membranes (FAA-3-50 and Orion TM1) and polyphenylene-based block copolymer (QPP-6F) were used.

MeV carbon ion irradiation-induced changes in the electrical conductivity of silver nanowire networks

Bushra Bari,Shehla Honey,Madhuku Morgan,Ishaq Ahmad,Rauf Khan,Arshad Muhammad,Khalid Alamgir,Shahzad Naseem,Maaza Malik 한국물리학회 2015 Current Applied Physics Vol.15 No.5

MeV carbon ion irradiation-induced changes in the electrical conductivity of Silver nanowire (Ag-NW) networks is demonstrated systematically at different C+ ion fluences ranging from 1 × 1012 to 1 × 1016 ions/cm2 at room temperature. At low C+ ion fluences, the electrical conductivity of Ag-NWs decreases and subsequently increases with increase fluence. Finally, at high C+ ion fluences, conductivity again decreases. The variation in the electrical conductivity of Ag NW network is discussed after analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The observed increase in electrical conductivity is thought to be due to ion induced coalescence of Ag-NWs at contact position, which causes reduction of wire-wire contact resistance, while the decrease in electrical conductivity may be due to defect production by C+ ions into Ag-NWs. Ion beam technology is therefore a very promising technology that is capable of fabricating highly conductive Ag-NW networks for transparent electrodes. Moreover, a method for thinning, slicing and cutting of Ag-NWs using ion beam technology is also reported.

EC 기준 파프리카 순환식 수경재배에서 양액 교체 주기에 따른 양액 중의 이온 균형 및 각 이온의 EC 기여도 변화

안태인(Tae In Ahn),손정익(Jung Eek Son) 한국원예학회 2011 원예과학기술지 Vol.29 No.1

EC 기준의 순환식 수경재배시스템에서 재사용 양액 내의 이온 농도의 변화와 각 이온의 EC 기여 비율의 변화는 안정적인 양액 관리를 위해서 고려되어야 할 중요한 요인이다. 본 연구는 초기 생육단계 파프리카의 EC 기준 순환식 수경 재배에서 교체 주기에 따른 재사용 양액 내 이온 농도, 이온균형 및 이온의 EC 기여도의 변화를 조사하여 재사용 양액의 적정 분석 주기를 규명하고자 수행하였다. 실험은 파프리카의 평균 마디수가 13마디일 때 시작하였고, 처리 종료 시점에서는 평균 마디수가 18마디였다. 1개의 암면 슬라브당 3주의 파프리카가 재배되었다. 처리는 재사용 양액의 교체 주기에 따라 각각 1주, 2주, 3주, 4주 교체 처리구로 구성되었다. 양액은 일사비례제어방식으로 급액되었다. 배액은 배액 탱크에 수집된 후에 당일 관수가 종료된 후 혼합 탱크에서 EC 2.69dS · m?¹가 될 때까지 희석되었다. 혼합된 양액은 익일의 양액으로 사용되었다. 재사용 양액은 주기적으로 수집하여 분석되었다. 교체 주기에 따른 이온 농도의 변화는 처리별 차이가 나타나지 않았다. 모든 처리구에서 이온 농도의 변화 범위는 각각 K? 5-8, Ca²? 11-14, Mg²? 2.0-2.7, Na? 0.5-0.6, NO₃? 14-19, SO₄²? 4-5, PO₄³? 1-4, Cl? 0.3-0.5meq · L?¹와 같았다. 교체 주기에 따른 이온 균형 변화는 크지 않았다. 그러나 전체 처리구에서 이온 비율의 변화는 일정한 경향을 나타냈다. 양이온 비율 변화는 K? : Ca²?을 중심으로 나타났으며, 음이온은 SO₄²? : PO₄³?를 중심으로 나타났다. 양액 중의 K³, NO₃?, H₂PO₄?의 1가 이온과 Ca²?, Mg²?, SO₄²?의 2가 이온의 활동도 계수는 각각 0.8-0.9, 0.5-0.6 사이에서 변하였고, 시간 경과와 함께 각 이온의 활동도 계수는 일정한 경향을 나타냈다. 각 이온이 양액의 EC에 기여한 비율은 K?와 NO₃?가 가장 컸고, 다음으로 Ca²?, SO₄²?, Mg²? 순으로 나타났다. 본 실험에 적용한 교체 주기 4주는 초기 생육단계의 파프리카를 EC 기준 순환식으로 수경재배 할 경우, 이온 농도 변화와 이에 따른 EC 기여도의 변화는 안정적인 범위 이내라고 판단된다. Individual ion concentrations and ionic contributions to EC reading in the circulated nutrient solution are the important factors to be considered for stable EC-based closed-loop soilless culture. This study was conducted to determine appropriate ion-analysis intervals of the circulated nutrient solutions based on ion concentration, ion balance, and ion electrical conductivity under different renewal intervals in EC-based nutrient control systems for sweet peppers (Capsicum annum L. ‘Fiesta’) in early growth stage. Average node numbers of the plants were 13 and 18 when the experiment started and finished, respectively, and three plants were grown in each rockwool slab. Four different renewal intervals of circulated nutrient solutions such as 1, 2, 3, and 4 weeks were used as treatment. Nutrient solutions were supplied to the plants based on integrated radiation. Drainage was collected into drain tanks after irrigation ended in the day and then mixed with fresh water until the EC reaches 2.69 dS · m?¹. The replenished nutrient solution was supplied to the plants in the next day. Ion concentrations of the individual ions periodically analyzed in the circulated nutrient solutions showed no significant differences among the treatments during the experimental period. Ion concentrations of K?, Ca²?, Mg²?, Na?, NO₃?, SO₄²?, PO₄³?, and Cl? varied within 5-8, 11-14, 2.0-2.7, 0.5-0.6, 14-19, 4-5, 1-4, and 0.3-0.5 meq · L?¹, respectively. Ion balance showed a consistent tendency over all the treatments and especially K? : Ca²? and SO₄²? : PO₄³? played great roles in the cation and anion balances in the nutrient solutions, respectively. Activity coefficients of ions such as K³, NO₃?, and H₂PO₄? varied within 0.8-0.9 and those of Ca²?, Mg²?, SO₄²? varied within 0.5-0.6, showing little changes with time. Ionic contributions of K? and NO₃? to EC reading were the greatest followed by Ca²?, SO₄²?, and Mg²? in the order. From the results, we thought that allowable ranges in ion concentration, ion balance, and subsequent individual ionic contributions to EC reading would be obtained within 4-week renewal interval of nutrient solution in EC-based closed-loop soilless culture for sweet pepper plants.

SPPO pore-filled composite membranes with electrically aligned ion channels via a lab-scale continuous caster for fuel cells: An optimal DC electric field strength-IEC relationship

Lee, Ju-Hyuk,Lee, Ju-Young,Kim, Jae-Hun,Joo, Jiyong,Maurya, Sandip,Choun, Myounghoon,Lee, Jaeyoung,Moon, Seung-Hyeon Elsevier 2016 Journal of membrane science Vol.501 No.-

<P><B>Abstract</B></P> <P>In this paper, novel composite membranes with electrically aligned ion channels in the thickness direction are presented for fuel cell applications; a fabrication method in the scale-up system and continuous mode is also suggested. The sulfonated poly(2,6-dimethyl-1,4-phenlyene oxide) (SPPO) polymer filled porous polyethylene (ρPE) films were prepared using a lab-scale continuous caster and simultaneously a direct-current (DC) electric field was applied for the alignment of ion channels in SPPO. Importantly, the proton conductivity of aligned-composite membranes with various ion exchange capacities was enhanced by three to five times than the non-aligned SPPO composite membranes. Finally, the optimized aligned composite membranes with the highest transport number were only applied for the fuel cell test. The optimized aligned composite membrane revealed the highest maximum power density than other fabricated composite membranes and Nafion® 115. Especially, the normalized maximum power density for unit conductivity value was introduced to confirm the effects of alignment of ion channels in a practical electrochemical system. The normalized maximum power density for unit conductivity value for the optimized aligned composite membrane was also stood 43% higher than that of Nafion® 212. According to all properties in this study, understanding the technique of alignment the ion channel in composite membranes offers a great possibility for improving the performance of the ion exchange membrane.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aligned pore-filled membranes were prepared under a DC electric field. </LI> <LI> Fabrication of aligned composite membrane in the continuous and scale-up modes. </LI> <LI> The through-plane proton conductivity was enhanced up to five times. </LI> <LI> The optimum DC electric field strength was related to IEC range. </LI> <LI> The aligned ion-channels led to improvement of maximum power density in fuel cells. </LI> </UL> </P>

Li‐ion hopping conduction enabled by associative Li‐salt in acetonitrile solutions

구본협,이혜진,박기성,황선욱,이호춘 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.2

To date, ionic conduction in nonaqueous electrolytes has been explained through the vehicle-type migration mechanism. Yet, new research hints at another conduction mode: ion-hopping, seen in highly concentrated solutions with multi-coordinating solvents. Our research uncovers that Li-ion hopping conduction also occurs in monodentate acetonitrile (AN) electrolytes, enabled by a highly associative Li-salt. Using techniques like pulse-field gradient NMR, Raman spectroscopy, and dielectric relaxation spectroscopy, we examined AN solutions with lithium trifluoroacetate (LiTFA) and lithium bis(fluorosulfonyl) imide (LiFSI). Results showed that Li-ion diffusion in LiTFA-AN was faster due to an anion-bridge structure formed by the associative nature of LiTFA. In contrast, the LiFSI-AN solution demonstrated slower Li-ion movement. In practical applications, like LiFePO4 symmetric cells, 4 M LiTFA-AN outperformed 1 M LiTFA-AN in rate performance, despite its lower ionic conductivity. This challenges the belief that associative Li-salts are unsuitable for battery electrolytes and prompts reconsideration of other associative Li-salts. To date, ionic conduction in nonaqueous electrolytes has been explained through the vehicle‐type migration mechanism. Yet, new research hints at another conduction mode: ion‐hopping, seen in highly concentrated solutions with multi‐coordinating solvents. Our research uncovers that Li‐ion hopping conduction also occurs in monodentate acetonitrile (AN) electrolytes, enabled by a highly associative Li‐salt. Using techniques like pulse‐field gradient NMR, Raman spectroscopy, and dielectric relaxation spectroscopy, we examined AN solutions with lithium trifluoroacetate (LiTFA) and lithium bis(fluorosulfonyl)imide (LiFSI). Results showed that Li‐ion diffusion in LiTFA‐AN was faster due to an anion‐bridge structure formed by the associative nature of LiTFA. In contrast, the LiFSI‐AN solution demonstrated slower Li‐ion movement. In practical applications, like LiFePO 4 symmetric cells, 4 M LiTFA‐AN outperformed 1 M LiTFA‐AN in rate performance, despite its lower ionic conductivity. This challenges the belief that associative Li‐salts are unsuitable for battery electrolytes and prompts reconsideration of other associative Li‐salts.

고분자전해질 연료전지에서 고분자 막의 이온 전도도

황병찬 ( Byungchan Hwang ),정회범 ( Hoi Bum Chung ),이무석 ( Moo Seok Lee ),이동훈 ( Dong Hoon Lee ),박권필 ( Kwonpil Park ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.5

고분자전해질 연료전지에서 전해질막의 이온전도도에 미치는 상대습도, 전류밀도, 온도의 영향에 대해 연구하였다. 전해질막의 물의 함량과 물의 이동은 이온전도도에 많은 영향을 미친다. 전기삼투와 역확산만으로 물 이동을 모사하고 해석하였다. 이온전도도는 셀 밖에서 측정 장비로 막 상태에서 그리고 막전극합체로 구동상에서 측정되었다. 상대습도 증가에 따라 막 내 물 함량이 증가하였고 물 함량 증가에 따라 이온전도도도 상승하였다. 전류밀도 증가에 따라 전기삼투와 역확산에 의한 물의 양이 증가해 물 함량이 선형적으로 증가하였고 그 결과 전류밀도 증가에 따라 이온전 도도가 선형적으로 상승하였다. 온도가 50 oC에서 80 oC로 증가함에 따라 이온전도도는 약 40% 증가하였다. The effects of relative humidity, current density and temperature on the ionic conductivity were studied in PEMFC (Proton Exchange Membrane Fuel Cell). Water contents and water flux in the electrolyte membrane largely affected ion conductivity. The water flux was modelled and simulated by only electro-osmotic drag and back-diffusion of water. Ion conductivities were measured at membrane state out of cell and measured at MEA (Membrane and Electrode Assembly) state in condition of operation. The water contents in membrane increase as relative humidity increased in PEMFC, as a results of which ion conductivity increased. Current enhanced electro-osmotic drag and back diffusion and then water contents linearly increased. Enhancement of current density results in ion conductivity. Ion conductivity of about 40% increased as the temperature increased from 50 oC to 80 oC.

Origin of excellent rate and cycle performance of Na⁺-solvent cointercalated graphite vs. poor performance of Li⁺-solvent case

Jung, Sung Chul,Kang, Yong-Ju,Han, Young-Kyu Elsevier 2017 Nano energy Vol.34 No.-

<P><B>Abstract</B></P> <P>Despite its high reversibility for Li<SUP>+</SUP> intercalation, graphite is known to be electrochemically inactive for Na<SUP>+</SUP> intercalation. On the contrary, recent studies have demonstrated that graphite is active and shows excellent rate and cycle performance for Na<SUP>+</SUP>-solvent cointercalation but it exhibits poor performance for Li<SUP>+</SUP>-solvent cointercalation. Herein, we elucidate the mechanism of Li<SUP>+</SUP>- and Na<SUP>+</SUP>-solvent cointercalation into graphite and the origin of the strikingly different electrochemical performance of Li<SUP>+</SUP>- and Na<SUP>+</SUP>-solvent cointercalation cells. Na<SUP>+</SUP> intercalation into graphite is thermodynamically unfavorable, but Na<SUP>+</SUP>-diglyme cointercalation is very favorable. The diglyme–graphene van der Waals interaction reinforces the interlayer coupling strength and thereby improves the resistance of graphite to exfoliation. The transport of solvated Na ions is so fast that the diffusivity of Na<SUP>+</SUP>-diglyme complexes is markedly faster (by five orders of magnitude) than that of Li<SUP>+</SUP>-diglyme complexes. The very fast Na<SUP>+</SUP>-diglyme conductivity is attributed to facile sliding of flat diglyme molecules, which completely solvate Na ions in the interlayer space of graphite. The slow Li<SUP>+</SUP>-diglyme conductivity is ascribed to steric hindrance to codiffusion caused by bent diglyme molecules that incompletely solvate Li ions. The bent and flat diglyme molecules surrounding Li and Na ions, respectively, are highly associated with the strong Li<SUP>+</SUP>–graphene and weak Na<SUP>+</SUP>–graphene interactions, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Li<SUP>+</SUP>- and Na<SUP>+</SUP>-solvent cointercalations into graphite were examined. </LI> <LI> Solvent cointercalation enables Na<SUP>+</SUP> intercalation into graphite thermodynamically. </LI> <LI> Na<SUP>+</SUP>-solvent transport is strikingly faster than Li<SUP>+</SUP>-solvent transport. </LI> <LI> Weak Na<SUP>+</SUP> ion–graphene interaction significantly enhances rate capability. </LI> <LI> Slow Li<SUP>+</SUP>-diglyme conductivity is ascribed to steric hindrance to codiffusion. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Sodium Ion Diffusion in Al₂O₃: A Distinct Perspective Compared with Lithium Ion Diffusion

Jung, Sung Chul,Kim, Hyung-Jin,Choi, Jang Wook,Han, Young-Kyu American Chemical Society 2014 NANO LETTERS Vol.14 No.11

<P>Surface coating of active materials has been one of the most effective strategies to mitigate undesirable side reactions and thereby improve the overall battery performance. In this direction, aluminum oxide (Al<SUB>2</SUB>O<SUB>3</SUB>) is one of the most widely adopted coating materials due to its easy synthesis and low material cost. Nevertheless, the effect of Al<SUB>2</SUB>O<SUB>3</SUB> coating on carrier ion diffusion has been investigated mainly for Li ion batteries, and the corresponding understanding for emerging Na ion batteries is currently missing. Using ab initio molecular dynamics calculations, herein, we first find that, unlike lithiation, sodiation of Al<SUB>2</SUB>O<SUB>3</SUB> is thermodynamically unfavorable. Nonetheless, there can still exist a threshold in the Na ion content in Al<SUB>2</SUB>O<SUB>3</SUB> before further diffusion into the adjacent active material, delivering a new insight that both thermodynamics and kinetics should be taken into account to describe ionic diffusion in any material media. Furthermore, Na ion diffusivity in Na<SUB><I>x</I></SUB>Al<SUB>2</SUB>O<SUB>3</SUB> turns out to be much higher than Li ion diffusivity in Li<SUB><I>x</I></SUB>Al<SUB>2</SUB>O<SUB>3</SUB>, a result opposite to the conventional stereotype based on the atomic radius consideration. While hopping between the O-rich trapping sites via an Na–O bond breaking/making process is identified as the main Na ion diffusion mechanism, the weaker Na–O bond strength than the Li–O counterpart turns out to be the origin of the superior diffusivity of Na ions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-11/nl503169v/production/images/medium/nl-2014-03169v_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl503169v'>ACS Electronic Supporting Info</A></P>

Improved electrochemical, mechanical and transport properties of novel lithium bisnonafluoro-1-butanesulfonimidate (LiBNFSI) based solid polymer electrolytes for rechargeable lithium ion batteries

Karuppasamy, K.,Kim, Dongkyu,Kang, Yong Hee,Prasanna, K.,Rhee, Hee Woo Elsevier 2017 Journal of industrial and engineering chemistry Vol.52 No.-

<P><B>Abstract</B></P> <P>In the present work, a new methodology for improving the ionic conductivity and cation transport properties of polymer electrolytes have been synthesized by adding bulky anion based novel lithium bisnonafluoro-1-butanesulfonimidate salt and characterized for its applications in lithium ion batteries. The self-standing solid polymer electrolyte films exhibit excellent mechanical, thermal, and electrochemical stability. The ion–polymer interactions are examined thoroughly by ATR Fourier Transform-Infra Red Spectroscopy. The solid polymer electrolyte prepared with EO/Li ratio 14 exhibits a highest ionic conductivity of 10<SUP>−4</SUP> Scm<SUP>−1</SUP> at 333K. Also, it achieves a maximum lithium transference number of 0.31 and it is electrochemically stable in the scanned electrochemical window. This new type of polymer electrolytes with high ion conductivity and improved mechanical properties paves way to be a potential candidate along with lithium anode and LiCoO<SUB>2</SUB> cathode in the lithium ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel LiBNFSI based SPEs have been prepared and characterized for its applications in lithium ion batteries. </LI> <LI> The prepared self-standing SPE films exhibit excellent mechanical, thermal, and electrochemical stability. </LI> <LI> These electrolytes give maximum ionic conductivity and electrochemical stability at ambient temperature. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

LiAlH4-PVDF 전해질 복합체의 열확산 및 전기화학적 특성평가

황준현,홍태환 한국수소및신에너지학회 2022 한국수소 및 신에너지학회논문집 Vol.33 No.5

A lithium-ion battery exhibits high energy density but has many limitations due to safety issues. Currently, as a solution for this, research on solid state batteries is attracting attention and is actively being conducted. Among the solid electrolytes, sulfide-based solid electrolytes are receiving much attention with high ion conductivity, but there is a limit to commercialization due to the relatively high price of lithium sulfide, which is a precursor material. This study focused on the possibility of relatively inexpensive and light lithium hydride and conducted an experiment on it. In order to analyze the characteristics of LiAlH4, ion conductivity and thermal stability were measured, and a composites mixed with PVDF, a representative polymer electrolyte, was synthesized to confirm a change in characteristics. And metallurgical changes in the material were performed through XRD, SEM, and BET analysis, and ion conductivity and thermal stability were measured by EIS and LFA methods. As a result, Li3AlH6 having ion conductivity higher than LiAlH4 is formed by the synthesis of composite materials, and thus ion conductivity is slightly improved, but thermal stability is rapidly degraded due to structural irregularity.