패턴전사 프린팅을 활용한 리튬이온 배터리 양극 기초소재 Li₂CO₃의 나노스케일 패턴화 방법

강영림,박태완,박은수,이정훈,왕제필,박운익,Kang, Young Lim,Park, Tae Wan,Park, Eun-Soo,Lee, Junghoon,Wang, Jei-Pil,Park, Woon Ik 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.4

지난 수십년간 인류에게 핵심적인 에너지 자원이었던 화석연료가 갈수록 고갈되고 있고, 산업발전에 따른 오염이 심해지고 있는 환경을 보호하기 위한 노력의 일환으로, 친환경 이차전지, 수소발생 에너지 장치, 에너지 저장 시스템 등과 관련한 새로운 에너지 기술들이 개발되고 있다. 그 중에서도 리튬이온 배터리 (Lithium ion battery, LIB)는 높은 에너지 밀도와 긴 수명으로 인해, 대용량 배터리로 응용하기에 적합하고 산업적 응용이 가능한 차세대 에너지 장치로 여겨진다. 하지만, 친환경 전기 자동차, 드론 등 증가하는 배터리 시장을 고려할 때, 수명이 다한 이유로 어느 순간부터 많은 양의 배터리 폐기물이 쏟아져 나올 것으로 예상된다. 이를 대비하기 위해, 폐전지에서 리튬 및 각종 유가금속을 회수하는 공정개발이 요구되는 동시에, 이를 재활용할 수 있는 방안이 사회적으로 요구된다. 본 연구에서는, 폐전지의 재활용 전략소재 중 하나인, 리튬이온 배터리의 대표적 양극 소재 Li2CO3의 나노스케일 패턴 제조 방법을 소개하고자 한다. 우선, Li2CO3 분말을 진공 내 가압하여 성형하고, 고온 소결을 통하여 매우 순수한 Li2CO3 박막 증착용 3인치 스퍼터 타겟을 성공적으로 제작하였다. 해당 타겟을 스퍼터 장비에 장착하여, 나노 패턴전사 프린팅 공정을 이용하여 250 nm 선 폭을 갖는, 매우 잘 정렬된 Li2CO3 라인 패턴을 SiO2/Si 기판 위에 성공적으로 형성할 수 있었다. 뿐만 아니라, 패턴전사 프린팅 공정을 기반으로, 금속, 유리, 유연 고분자 기판, 그리고 굴곡진 고글의 표면에까지 Li2CO3 라인 패턴을 성공적으로 형성하였다. 해당 결과물은 향후, 배터리 소자에 사용되는 다양한 기능성 소재의 박막화에 응용될 것으로 기대되고, 특히 다양한 기판 위에서의 리튬이온 배터리 소자의 성능 향상에 도움이 될 것으로 기대된다. For the past few decades, as part of efforts to protect the environment where fossil fuels, which have been a key energy resource for mankind, are becoming increasingly depleted and pollution due to industrial development, ecofriendly secondary batteries, hydrogen generating energy devices, energy storage systems, and many other new energy technologies are being developed. Among them, the lithium-ion battery (LIB) is considered to be a next-generation energy device suitable for application as a large-capacity battery and capable of industrial application due to its high energy density and long lifespan. However, considering the growing battery market such as eco-friendly electric vehicles and drones, it is expected that a large amount of battery waste will spill out from some point due to the end of life. In order to prepare for this situation, development of a process for recovering lithium and various valuable metals from waste batteries is required, and at the same time, a plan to recycle them is socially required. In this study, we introduce a nanoscale pattern transfer printing (NTP) process of Li2CO3, a representative anode material for lithium ion batteries, one of the strategic materials for recycling waste batteries. First, Li2CO3 powder was formed by pressing in a vacuum, and a 3-inch sputter target for very pure Li2CO3 thin film deposition was successfully produced through high-temperature sintering. The target was mounted on a sputtering device, and a well-ordered Li2CO3 line pattern with a width of 250 nm was successfully obtained on the Si substrate using the NTP process. In addition, based on the nTP method, the periodic Li2CO3 line patterns were formed on the surfaces of metal, glass, flexible polymer substrates, and even curved goggles. These results are expected to be applied to the thin films of various functional materials used in battery devices in the future, and is also expected to be particularly helpful in improving the performance of lithium-ion battery devices on various substrates.

CFD 해석을 적용한 18650 리튬-이온 배터리 팩의 열 해석 신뢰도 기초 분석

심창휘,김한상 한국수소및신에너지학회 2020 한국수소 및 신에너지학회논문집 Vol.31 No.5

The Li-ion battery is considered to be one of the potential power sources for electric vehicles. In fact, the efficiency, reliability, and cycle life of Li-ion batteries are highly influenced by their thermal conditions. Therefore, a novel thermal management system is highly required to simultaneously achieve high performance and long life of the battery pack. Basically, thermal modeling is a key issue for the novel thermal management of Li-ion battery systems. In this paper, as a basic study for battery thermal modeling, temperature distributions inside the simple Li-ion battery pack (comprises of nine 18650 Li-ion batteries) under a 1C discharging condition were investigated using measurement and computational fluid dynamics (CFD) simulation approaches. The heat flux boundary conditions of battery cells for the CFD thermal analysis of battery pack were provided by the measurement of single battery cell temperature. The temperature distribution inside the battery pack were compared at six monitoring locations. Results show that the accurate estimation of heat flux at the surface of single cylindrical battery is paramount to the prediction of temperature distributions inside the Li-ion battery under various discharging conditions (C-rates). It is considered that the research approach for the estimation of temperature distribution used in this study can be used as a basic tool to understand the thermal behavior of Li-ion battery pack for the construction of effective battery thermal management systems.

The characterization of dynamic behavior of Li-ion battery packs for enhanced design and states identification

Nam, Woochul,Kim, Ji-Young,Oh, Ki-Yong Elsevier 2018 Energy conversion and management Vol.162 No.-

<P><B>Abstract</B></P> <P>The dynamic responses of a Li-ion battery pack deployed on hybrid electric vehicles are studied with a high fidelity finite element model and a parametric reduced-order model. The effects of microstructure transformation in the electrode materials caused by lithium-ion intercalation/deintercalation on the evolution of dynamic responses are investigated including the effects of the state of charge, aging, and cell-to-cell variations. The dynamic responses obtained from a finite element analysis show two interesting phenomena. First, the high modal density is controllable with the design modification of a pack component. Second, dynamic responses, especially the evolution of the natural frequencies of the fixed-boundary modes, of a Li-ion battery pack provide useful information to estimate the dynamic states or health states of the battery. A probabilistic analysis is also carried out considering stochastic operational conditions of hybrid electric vehicles with a parametric reduced-order model. The probabilistic analysis not only suggests appropriate modes and locations for monitoring its dynamic responses, but also determines the maximum response level of every cell in the battery pack. The proposed modeling approach can improve the safety and reliability of the structural design of battery cells and packs. Furthermore, it can be useful for the identification of the battery states during the operation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dynamics of the battery pack are characterized for various operational conditions. </LI> <LI> Statistical structural variations are analyzed using an order reduction technique. </LI> <LI> Proper design of the spacers can eliminate concerns on high modal density. </LI> <LI> Fixed-boundary modes are sensitive to the evolution of structural dynamics. </LI> <LI> Probabilistic analysis defines sensitive locations for monitoring a battery pack. </LI> </UL> </P>

리튬이온(폴리머) 배터리의 화재위험성 연구

김창수,전형훈,김명관,정용식 한국화재감식학회 2020 한국화재감식학회 학회지 Vol.11 No.3

Because Li-ion battery and Li-Polymer battery have high-energy storage density, they are used for various electronic devices such as electronic cigarette, electronic bicycle, drone, second battery, even golf cart and electronic car. Recently, however, battery explosion is sometimes occurring on electronic devices using Li-ion battery and is becoming serious as bodily harm is breaking out due to explosion. For this, this paper described the Li-ion Battery’s operating principles and Fire was caused through previous research and re-testing based on exposure to foreign substances such as water from the battery in contrast. According to the these experiments, we conducted a study to develope scanning techniques of fire and safety measures. (Most previous studies have been about the risk of fire in the battery due to physical shock, overcharging, and high temperature exposure.)

Significance of ferroelectric polarization in poly (vinylidene difluoride) binder for high-rate Li-ion diffusion

Song, Woo-Jin,Joo, Se Hun,Kim, Do Hyeong,Hwang, Chihyun,Jung, Gwan Yeong,Bae, Sohyeon,Son, Yeonguk,Cho, Jaephil,Song, Hyun-Kon,Kwak, Sang Kyu,Park, Soojin,Kang, Seok Ju Elsevier 2017 Nano energy Vol.32 No.-

<P><B>Abstract</B></P> <P>An interesting and effective route for improving battery performance using ferroelectric poly(vinylidene difluoride) (PVDF) polymer as a binder material is demonstrated in this work. A ferroelectric PVDF phase developed under the appropriate thermal annealing process enables generation of suitable polarization on active materials during the discharge and charge process, giving rise to longer capacity with lower overpotential at a high current rate. Electrochemical analysis including <I>in situ</I> galvanostatic electrochemical impedance spectroscopy and a galvanostatic intermittent titration measurement revealed that the ferroelectric binder effectively reduced Li-ion diffusion resistance and supported fast migration in the vicinity of active electrodes. Computational results further support that the binding affinity of the ferroelectric PVDF surface is much higher than that of the paraelectric PVDF, confirmed by ideally formed ferroelectric and paraelectric PVDF conformations with Li-ions. Furthermore, we consistently achieved high Li-ion battery (LIB) performance in full cell architecture consisting of a LTO/separator/LFP with a ferroelectric PVDF binder in the anode and cathode materials, revealing that the polarization field is important for fabricating high-performance LIBs, potentially opening a new design concept for binder materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The ferroelectric polarization in PVDF binder enhances Li-ions diffusion. </LI> <LI> Excellent rate performance is demonstrated by β-phase of PVDF binder </LI> <LI> In depth computational study exhibits the polarization effect of ferroelectric binder in LIB cell. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>We demonstrate the effect of PVDF polarization in lithium ion battery system. The strong polarization of ferroelectric PVDF binder on the active material enhances the transport of Li-ion during charge and discharge. As results, the Li-ion diffusion by ferroelectric phase leads to excellent rate performance and cycling stability compared to paraelectric PVDF binder.</P> <P>[DISPLAY OMISSION]</P>

Ternary lithium molybdenum oxide, Li₂Mo₄O₁₃: A new potential anode material for high-performance rechargeable lithium-ion batteries

Verma, Rakesh,Park, Chan-Jin,Kothandaraman, R.,Varadaraju, U.V. Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>The need to identify lithium ion battery anodes consisting of new materials that display high energy density and good cycling stability has interested the research on reversible so-called conversion reaction between lithium and molybdenum oxides such as ternary metal oxide (Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB>). Polycrystalline Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> was synthesized by conventional solid-state reaction route and explored as new potential anode material for secondary lithium ion battery applications <I>vs.</I> Li<SUP>+</SUP>/Li in half-cell mode. The electrochemical performance of the Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> electrode was studied by cyclic voltammograms and galvanostatic discharge-charge cycling under different rates. In the working voltage between 2.5 V and 0.1 V, Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> shows a high first charge capacity of 1062 mAh g<SUP>−1</SUP> at current rate of C/10 (24 Li react with 10 h) and a superior rate capability with capacity retention of 1008, 842, 713 and 640 mAh g<SUP>−1</SUP> under current rates of C/10, C/5, C/3 and C/2 (24Li react with in 2 h), respectively. Further, the cycling performance was evaluated at C/3 rate (424 mA g<SUP>−1</SUP>) and after 100 cycles a reversible capacity of 550 mAh g<SUP>−1</SUP> was obtained with columbic efficiency of ∼100%. Ex-situ XRD studies confirmed that the electrochemical reaction involves insertion of 5Li/f.u <I>vs.</I> Li<SUP>+</SUP>/Li during discharge to 1.3 V and the crystal structure was retained when charged to 2.5 V. Below 0.8 V, conversion reaction occurs leading to amorphization of the phase. When discharged to 0.1 V, Mo<SUP>+6</SUP> is reduced to Mo<SUP>0</SUP> state on the basis of the conversion reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A ternary lithium molybdenum oxide (Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB>) is explored as anode for lithium ion battery for the first time. </LI> <LI> Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> phase shows excellent electrochemical performance possibly due to the apriori presence of the active ions in the lattice. </LI> <LI> Li<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> shows high capacity, excellent rate capability and cycling. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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>

F-doped Li_1.15Ni_0.275Ru_0.575O₂ cathode materials with long cycle life and improved rate performance

Choi, Sojeong,Kim, Min-Cheol,Moon, Sang-Hyun,Kim, Hyeona,Park, Kyung-Won Elsevier 2019 ELECTROCHIMICA ACTA Vol.326 No.-

<P><B>Abstract</B></P> <P>In this study, Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> cathode material for lithium-ion batteries is synthesized using a facile solid-state reaction. In particular, the Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> cathode material with a layered structure, despite its high initial capacity, deteriorates in both stability and rate performance. In order to overcome the drawbacks, F-doped Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> cathode structures (LNROF-x, 0 < x < 0.1) are prepared with varying contents of F as a dopant and characterized. For the F-doped Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> samples, if the O<SUP>2−</SUP> sites in the structure are replaced by F<SUP>−</SUP>, the transition metal ions of Ni<SUP>2+</SUP> and Ru<SUP>4+</SUP> can be partially reduced to Ni<SUP>+</SUP> and Ru<SUP>3+</SUP> with larger ionic radii for charge compensation. Thus, the increased interspace between the transition metal ions caused by their reduction increases the lattice parameter in the F-doped Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> structure. Compared to the undoped Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB>, the improved electrochemical properties, i.e., long life cycle and rate performance, of the F-doped Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> samples can result from the improved structural stability caused by a stronger bond of metal-F than that of metal-O and an increased Li<SUP>+</SUP>-ion diffusion motion caused by an increased Li slab distance. Furthermore, the Li<SUP>+</SUP>-ion diffusion coefficients for the samples are measured by cyclic voltammetry and galvanostatic intermittent titration. However, with increasing F-doping amount, the diffusion coefficients for LNROF-0.02, LNROF-0.04, and LNROF-0.06 increase, whereas the diffusion coefficient for LNROF-0.08 with the excessive F-doping decreases because of the increased resistance to Li<SUP>+</SUP> ion motion caused by the Li/Ni anti-site defect. Thus, the amount of F as a dopant in the F-doped Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> samples for the LIBs needs to be optimized.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Li<SUB>1.15</SUB>Ni<SUB>0.275</SUB>Ru<SUB>0.575</SUB>O<SUB>2</SUB> (LNRO) cathodes were synthesized using a solid-state reaction. </LI> <LI> F-doped LNRO cathodes were prepared with varying contents of F as a dopant. </LI> <LI> F-doped LNRO cathodes showed the improved electrochemical properties. </LI> <LI> The improved performance is due to a strong bond of metal-F and an increased Li + -ion diffusion motion. </LI> <LI> The amount of F as a dopant in the F-doped LNRO samples for the LIBs was optimized. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

N-functionalized graphene quantum dots: Charge transporting layer for high-rate and durable Li₄Ti₅O₁₂-based Li-ion battery

Khan, Firoz,Oh, Misol,Kim, Jae Hyun Elsevier 2019 Chemical engineering journal Vol.369 No.-

<P><B>Abstract</B></P> <P>Spinel Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> can replace carbon in Li-ion battery anodes due to its high voltage, preventing decomposition of the electrolyte and formation of Li metal dendrites. However, Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> has a low electronic conductivity and Li-ion diffusion coefficient, limiting its charge/discharge properties at high rate capacities, and also suffers from gassing during cycling. Here, we used N-functionalized graphene quantum dots interfacial layer, which (1) protects Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> from ambient degradation, (2) forms a thin and smooth solid-electrolyte interphase layer on the Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> surface, (3) acts as a charge transfer layer, (4) protects the Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> electrode from reactions with the electrolyte, and (5) suppresses gassing during cycling. Consequently, the Li-ion diffusion coefficient increased by ∼19%. The effectiveness of the N-functionalized graphene quantum dots is manifested in the specific capacity of 161 mAh/g at 50C, which is improved by ∼23% compared to pure Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> electrode and maintained for over 500 cycles. Unlike graphene, N-functionalized graphene quantum dots themselves work as a stable charge transporting and protecting layer. Our strategy successfully obtained a good cycling performance and long cycling life of Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> at high C-rates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel strategy was presented to enhance the performance of LTO electrode. </LI> <LI> N-GQDs were acted as protecting layer on LTO surface from interfacial reactions. </LI> <LI> The Li-ion diffusion coefficient was enhanced by ∼19%. </LI> <LI> The capacity was enhanced by ∼23% at 50C via encapsulation of LTO by N-GQDs. </LI> <LI> N-GQDs can suppress the gassing during the cycling process. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

PCM 종류에 따른 18650 리튬-이온 셀 모듈의 냉각 특성 연구

유시원,김한상 한국수소및신에너지학회 2020 한국수소 및 신에너지학회논문집 Vol.31 No.6

The performance and cost of electric vehicles (EVs) are much influenced by the performance and service life of the Li-ion battery system. In particular, the cell performance and reliability of Li-ion battery packs are highly dependent on their operating temperature. Therefore, a novel battery thermal management is crucial for Li-ion batteries owing to heat dissipation effects on their performance. Among various types of battery thermal management systems (BTMS'), the phase change material (PCM) based BTMS is considered to be a promising cooling system in terms of guaranteeing the performance and reliability of Li-ion batteries. This work is mainly concerned with the basic research on PCM based BTMS. In this paper, a basic experimental study on PCM based battery cooling system was performed. The main purpose of the present study is to present a comparison of two PCM-based cooling systems (n-Eicosane and n-Docosane) of the unit 18650 battery module. To this end, the simplified PCM-based Li-ion battery module with two 18650 batteries was designed and fabricated. The thermal behavior (such as temperature rise of the battery pack) with various discharge rates (c-rate) was mainly investigated and compared for two types of battery systems employing PCM-based cooling. It is considered that the results obtained from this study provide good fundamental data on screening the appropriate PCMs for future research on PCM based BTMS for EV applications.