격자 볼츠만법을 이용한 리튬이온전지의 전극내 전해액 함침현상에 관한 수치적 연구

이상건(Sang Gun Lee),전동협(Dong Hyup Jeon) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.4

리튬이온전지의 다공성 전극내에서 전해액 주입 후 발생하는 함침현상에 관하여 격자 볼츠만법을 이용하여 수치해석적으로 연구하였다. 다공성 전극은 전극 제조 중 압연공정을 거치므로 압축된 전극의 공극률과 두께변화가 발생하여 전해액 함침성에 영향을 미치게 된다. 본 연구에서는 2 차원 격자 볼츠만법을 통하여 압축률에 따른 전해액 분포와 포화도 변화를 제시하였다. 압축된 전극에서의 전해액 침투경로의 변화는 기공의 두께방향 크기 감소에 기인하며, 따라서 전극의 함침성이 크게 감소하였음을 확인하였다. The electrolyte wetting phenomena in the electrode of lithium ion battery is studied numerically using a multiphase lattice Boltzmann method (LBM). When a porous electrode is compressed during roll-pressing process, the porosity and thickness of the compressed electrode are changed, which can affect its wettability. In this study, the change in electrolyte distribution and degree of saturation as a result of varying the compression ratio are investigated with two-dimensional LBM approach. We found that changes in the electrolyte transport path are caused by a reduction in through-plane pore size and result in a decrease in the wettability of the compressed electrode.

버퍼 층을 이용한 RF 마그네트론 스퍼터 방법에 의한 Al:ZnO 박막의 성장

노영수,박동희,김태환,최지원,최원국,No, Young-Soo,Park, Dong-Hee,Kim, Tae-Whan,Choi, Ji-Won,Choi, Won-Kook 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.3

Al이 도핑된 투명 전도성 Al:ZnO (AZO) 박막에 대한 RF magnetron sputtering 증착 법을 이용한 저온 최적공정조건을 연구하였다. 투명전극 재료로써의 AZO 박막의 전기적, 결정학적 물성을 최대한 향상시키기 위해서, in-situ상태에서 유리기판상에 최적화된 증착 조건의 AZO 버퍼 층을 삽입하는 이중박막 구조를 제작하였다. RF 인가 전력 $50{\sim}60\;W$에서 증착된 버퍼층 위에 120 W의 RF 전력에서 성장한 AZO 박막의 경우, 비저항 $3.9{\times}10^{-4}{\Omega}cm$, 전하 캐리어농도 $1.22{\times}10^{21}/cm^3$, 홀 이동도 $9.9\;cm^2/Vs$의 전기적 특성을 보였다. 이러한 결과는 버퍼 층이 없는 기존의 단일 구조와 비슷하나, 전기적 비저항 특성을 약 30% 정도 향상시킬 수 있었으며, 전기적 특성의 향상 원인을 $Ar^+$ 이온의 입사 에너지의 변화에 따른 버퍼 층의 압축응력과 결정화 정도와의 의존성으로 설명하였다. The optimal condition of low temperature deposition of transparent conductive Al-doped zinc oxide (AZO) films is studied by RF magnetron sputtering method. To achieve enhanced-electrical property and good crystallites quality, we tried to deposit on glass using a two-step growth process. This process was to deposit AZO buffer layer with optimal growth condition on glass in-situ state. The AZO film grown at rf 120 W on buffer layer prepared at RF $50{\sim}60\;W$ shows the electrical resistivity $3.9{\times}10^{-4}{\Omega}cm$, Carrier concentration $1.22{\times}10^{21}/cm^3$, and mobility $9.9\;cm^2/Vs$ in these results, The crystallinity of AZO film on buffer layer was similar to that of AZO film on glass with no buffer later but the electrical properties of the AZO film were 30% improved than that of the AZO film with no buffer layer. Therefore, the cause of enhanced electrical properties was explained to be dependent on degree of crystallization and on buffer layer's compressive stress by variation of $Ar^+$ ion impinging energy.

다공성 전극의 압축률이 레독스흐름전지의 성능에 미치는 영향에 대한 수치해석적 연구

정대인 ( Daein Jeong ),정승훈 ( Seunghun Jung ) 한국액체미립화학회 2017 한국액체미립화학회지 Vol.22 No.2

When designing a redox flow battery system, compression of battery stack is required to prevent leakage of electrolyte and to reduce contact resistance between cell components. In addition, stack compression leads to deformation of the porous carbon electrode, which results in lower porosity and smaller cross-sectional area for electrolyte flow. In this paper, we inves-tigate the effects of electrode compression on the cell performance by applying multi-dimensional, transient model of all-vanadium redox flow battery (VRFB). Simulation result reveals that large compression leads to greater pressure drop through-out the electrodes, which requires large pumping power to circulate electrolyte while lowered ohmic resistance results in bet-ter power capability of the battery. Also, cell compression results in imbalance between anolyte and catholyte and convective crossover of vanadium ions through the separator due to large pressure difference between negative and positive electrodes. Although it is predicted that the battery power is quickly improved due to the reduced ohmic resistance, the capacity decay of the battery is accelerated in the long term operation when the battery cell is compressed. Therefore, it is important to opti-mize the battery performance by taking trade-off between power and capacity when designing VRFB system.

다공성 전극의 압축률이 레독스흐름전지의 성능에 미치는 영향

정승훈 ( Seunghun Jung ),정대인 ( Daein Jeong ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-

Research on renewable energy such as solar, wind, and hydropower is being accelerated to resolve environmental problem and fossil fuel depletion problem. Most of renewable energies, however, have a limitation such that they cannot immediately respond to the power load because of their irregular power production. To compensate this problem, energy storage systems (EES) is indispensable. Redox flow batteries (RFB) have attracted attention as a strong candidate for future ESS in recent years. RFBs produce or store electric energy in liquid electrolyte by means of electrochemical reaction in electrodes where redox couples react together (see Fig. 1). According to the redox couple, there are several types of RFBs such as Zinc/Bromine RFB, All-vanadium RFB, Fe/Cr RFB. Among them, allvanadium redox flow battery (VRFB) is considered to be closest to commercialization. VRFB uses vanadium ions in both electrolytes (in the negative electrolyte: V²⁺,V³⁺ in the positive electrolyte:VO²⁺, VO⁺). Because same reactant (vanadium) is used in both electrodes, VRFB can easily recover its performance even though the electrolyte is contaminated by reactant crossover. Furthermore, VRFB can sustain very long operational life time because it does not require catalyst in electrodes. In the present study, the compression effect of porous electrodes on the performance of VRFB is computationally investigated. To predict the performance and physico-chemical behavior of VRFB, multi-dimensional, computational models are developed. Several battery design parameters such as cross-sectional area of the flow inlet, the electrode porosity, reaction area of electrode, ionic and electronic conductivity are influenced by electrode compression, which results in mass transport, electric resistance and flow characteristics of VRFB. The present multi-dimensional VRFB model is composed of four coupled partial differential equations, which are simultaneously solved by means of computational fluid dynamics technique. Preliminary charging and discharging performance of a unit VRFB is presented in figure 2 when the carbon-felt electrodes (4mm thickness and 0.95 of porosity) are compressed from 0% to 50%. Basic observation reveals that increasing the compression ratio leads to large ionic resistance of electrodes, which results in lower capacity utilization through this study. Also, higher compression ratio causes large pressure gradient in thru-electrode direction. This pressure gradient brings about severe convective crossover of vanadium ions through the membrane.

양극 활물질 공극률 조절을 통한 리튬이차전지의 전기화학적 특성 최적화

임진솔,안진혁,장은광,서혜원,최회주,조국영 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

리튬이차전지는 다양한 이동형 전자기기의 전원 공급원으로써 가장 널리 사용되고 있는 전기화학에너지 변환 시스템이다. 하나의 장치에서 요구되는 에너지는 폭발적으로 증가하고 있다. 예로써 전기자동차와 같은 경우에는 중대형 규모의 에너지원이 요구되며 우수한 구동 성능을 보유하여야 한다. 특히 사이클 특성을 개선하기 위해 전지의 핵심 부품인 양극에 있어서 최대의 성능을 갖도록 하는 연구가 중요하다. 양극의 성능에 영향을 주는 요소들 중에서 공극률은 전극의 구동 특성에 영향을 미친다. 양극의 공극률을 조절하는 방법은 집전체에 캐스팅한 전극을 롤프레싱으로 압축하여 조절한다. 본 연구에서는 캐스팅된 양극에 압축을 통한 두께 제어로 공극률을 조절하였고, 제어된 공극률에 따른 양극의 구동 특성 평가를 진행하였다.

압착전해 탈수시스템의 전극구조에 따른 전류밀도분포 연구

이현주(Hyunju Lee),허덕재(Deog Jae Hur),송태규(Tae Gyu Song) 한국소음진동공학회 2019 한국소음진동공학회 학술대회논문집 Vol.2019 No.10