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The crucial issue of wettability in high-energy-density lithium-ion batteries (LIBs) has not been comprehensively addressed to date. To overcome the challenge, state-of-the-art LIBs employing a ceramic-coated separator improves the safety- and wettability-related aspects of LIBs. Here, we present a mechanistic study of the effects of a ceramic-coated layer (CCL) on electrode wettability and report the optimal position of the CCL in LIBs. The electrolyte wetting was investigated using the multiphase lattice Boltzmann method and electrochemical impedance spectroscopy for capturing the electrolyte-transport dynamics in porous electrodes and impedance spectra in pouch-type LIBs, respectively. Results indicate that the CCL caused the velocity vector to transport the electrolyte further, resulting in an increase in the wetting rate. Moreover, the location of the CCL considerably affected the wettability of the LIBs. This study provides mechanical insight into the design and fabrication of high-performance LIBs by incorporating CCLs.

Ni-rich NCM-based cathode materials have garnered significant research interest for the development of high-performance lithium-ion batteries (LIBs) owing to their high energy capacity and low cost. However, they undergo several electrochemical degradation reactions that deteriorate the cathode performance. To alleviate the deterioration of the cathode, researchers have adopted surface coating materials, especially Li3BO3 (LBO), which demonstrates a superior modification effect, for Ni-rich NCM. Here, we investigate the electrochemical characteristics of an LBO-coated Ni-rich NCM cathode via experimental and numerical approaches. The cathode is synthesized through a wet chemical deposition method, and electrochemical measurements are conducted using coin half-cells. To further understand the effect of coating layer on the electrochemical performance, we developed an electrode coating model with modifying the porous electrode model. The model employs an impurity layer (Li2CO3 and LiOH), a protective layer (LiF), and a coating layer (LBO) to predict the discharge performance of LIBs. The validation results of the model are consistent with the experimental results. Electrochemical prediction results demonstrate that the LBO-coated Ni-rich NCM cathode would increase the discharge capacity.

Couette–Taylor flow reactor is a mixing device that offers wide range of mixing regimes within a single reactor and operates in continuous flow mode. This reactor is recently used in manufacturing the cathode material of lithium ion batteries. Here, we simulate the agglomeration process of Li(NixMnyCoz)O2 particles using computational fluid dynamics. Quadrature method of moments is implemented for modeling of aggregation and breakage in Couette-Taylor flow reactor. We conduct an experiment of the preparation of Li(NixMnyCoz)O2 precursors, and the experimental data are compared with simulated results for the validation of numerical model. The predicted evolutions of mean particle size are well agreed with experimental data. For the practical application, we investigate the effects of density ratio of particle to fluid and initial volume fraction of particles on the particle size. The results show that the particle diameter increases with increasing of density ratio, but it decreases with increasing of initial volume fraction of particles. On the other hand, the particle sizes become similar at high rotational speed.

Using the multiphase lattice Boltzmann method (LBM), the liquid water transport dynamics is simulated in a gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells (PEMFCs). The effect of rib structure on the water invasion process in the micro-porous GDL is explored by comparing the two cases, i.e., with rib and without rib structures. The liquid water distribution and water saturation profile are presented to determine the wetting mechanism in the GDL. The results show that the liquid water transport in the GDL is strongly governed by capillary force and the rib structure plays a significant role on water distribution and water transport behavior in the GDL. Comparison of two cases confirms that the rib structure influences on the location of water breakthrough. The liquid water distribution and water saturation profile indicate that the high resistance force underneath the rib suppresses the growth of water cluster, resulting in the change of flow path. After water breakthrough, the liquid water distribution under the channel has little variation, whereas that under the rib continues to change. The predicted value of effective permeability is in good agreement with Carman-Kozeny correlation and experimental results in the literature. The results suggest that the LBM approach is an effective tool to investigate the water transport behavior in the GDL.

Design parameters of bipolar plate are greatly influencing the mass transfer in polymer electrolyte membrane fuel cells. Water accumulation in the catalyst layer and gas diffusion layer causes the mass transport limitation, resulting in an inhibition of gaseous reactant transport to the reaction sites. To carve out the mass transport problems, the optimum design of flow channel is essential with profound understanding of water transport phenomena. Here, we investigate the effect of channel-rib width on dynamic behavior of liquid water in a gas diffusion layer using the multiphase lattice Boltzmann method. We simulate the various channel-rib width configurations and compare the simulated results. We present the water saturation profile with temporal variations of water distribution and relative pressure distribution. The results show that the channel-rib width plays an important role on water transport dynamics in a gas diffusion layer as well as water breakthrough and creeping. The influence of channel-rib width becomes significant as it increases.

Wettability by the electrolyte is claimed to be one of the challenges in the development of high-performance lithium-ion batteries. Non-uniform wetting leads to inhomogeneous distribution of current density and unstable formation of solid electrolyte interface film. Incomplete wetting influences the cell performance and causes the formation of lithium plating in the anode, which leads to safety issue. Research has pointed out that insufficient wetting could be found in the electrode, and the wetting characteristics would be different in each electrode. Here we use lattice Boltzmann simulation to show the electrolyte distribution and understand the wetting characteristics in the cathode and anode. We develop a multiphase lattice Boltzmann model with the reconstruction of electrode microstructure using a stochastic generation method. We use a porous electrode model to identify the effect of wettability on the cell performance and to elucidate the dependence of capacity on the wettability. Our results would lead to more reliable lithium-ion battery designs, and establish a framework to inspect the wettability inside electrodes.

Economical and efficient carbon capture, utilization and sequestration technologies are essential for addressing the global challenge to reduce CO2 emissions. However, current CO2 conversion technologies cannot meet the economic and energy requirements due to the sluggish processes for CO2 sequestration. Herein, we rationally designed a membrane-free (MF) Mg-CO2 battery as an advanced approach to sequester CO2 emissions by generating electricity and value-added chemicals without any harmful by-products. The newly-developed MF Mg-CO2 battery operates based on the indirect utilization of CO2 with facile hydrogen generation process, which leads to electrochemical performance of 64.8 mW cm−2 with a high Faraday efficiency (>92.0%). Over the 80 discharge-charge cycles, the outstanding cycling performance with the generation of triple gases, e.g., H2(g) under discharge and O2/Cl2(g) under charge mode, was attained without any degradation.

Enhancing the electrolyte wetting has been claimed to be a great challenge in developing high-energy density and large-scale lithium-ion batteries (LIBs). Superb wettability ensures high-quality LIBs, but poor wettability incurs unstable capacity, shortened cycle life, and additional manufacturing cost. However, wettability issue has been understated so far, and associated breakthrough technology is not yet available. Here, we report the enhancement of electrode wettability by controlling the volume ratio of different-sized particles. We demonstrate the electrolyte transport behavior in a straightforward way, and investigate the effect of particle-size ratio on the cathode wettability in two aspects: with porosity preserved and by adding small particles. Results show that particle-size ratio and porosity greatly influence the electrode wettability. Electrolyte distribution and correlated pore-throat size distribution not only affect the wetting behavior but also pose crucial factors that determine the wetting speed. This study provides novel mechanistic insight into the electrolyte wetting process, and the results are one of the few published ones that give important information toward wettability enhancement.

This study investigated the variations of Taylor flow and particle residence time in a Taylor reactor according to the changes of angular velocity and inlet velocity using computational fluid dynamics technique. The results showed that the fluid in a reactor became unstable with an increase of angular velocity. The flow moved to the regions of CCF, TVF, WVF and MWVF resulting in an increase of Reynolds number. Accordingly, the flow characteristics were different for each regions. We confirmed that the inlet velocity influences the Taylor flow. The particle residence time and standard deviation increased with an increase of angular velocity and a decrease of inlet velocity.

Researchers worldwide endeavor to develop the thinner gas diffusion layers (GDLs), which are enabling to achieve high power-density polymer electrolyte membrane fuel cells (PEMFCs). A number of experiments have attempted to understand the underlying mechanisms in the GDL that are responsible for water management and performance improvement. Here, we investigate the effect of GDL thickness on the dynamic behavior of liquid water using a multiphase lattice Boltzmann method. Various GDL configurations are simulated aiming on the fundamental understanding of multiphase flow phenomena. We report results of water saturation, water distribution and relative pressure distribution inside the GDL to elucidate the impact of GDL thickness on the water transport behavior. Water breakthrough and water creeping that determine the water behavior are deeply studied. In addition, we investigate the influence of channel-rib (CR) structure on a thin GDL. Optimum CR width is pursued for the effective water removal from a thin GDL. The results and findings here are expected to lead to more reliable water management and related high-power technologies of PEMFCs.

Solid oxide fuel cells are designed to operate in a wide temperature range (600–1000 °C). Operation at high temperature enhances the cell performance, but retains intrinsic problems such as poor long-term stability and high manufacturing cost. Recent studies have directed to the operation in intermediate temperature with incorporating the anode-supported solid oxide fuel cells. Here, we investigate the performance of anode-supported solid oxide fuel cells using a computational fluid dynamics based open-source software. We develop a complete overpotential model based on open-source fuel cell code. This model predicts the cell performance and provides insight into the transport phenomena and electrochemical characteristics. To validate our numerical model, we compare the simulated results with experimental data at intermediate temperatures. The cell performance is decomposed into several component overpotentials to understand the contribution of each one on the overall potential loss. The reduction of electrolyte overpotential is explored to attain high performance at intermediate temperature by investigating the influence of the electrolyte thickness and alternative electrolyte material on the cell performance.

The effect of the compression ratio on the dynamic behavior of liquid water transport in a gas diffusion layer (GDL) is studied both experimentally and numerically. We experimentally study the emergence and growth of liquid droplets in a channel at various compression ratios by adopting a direct visualization device. The results of the experiment show that water breakthrough occurs at the channel for a low compression ratio, whereas it is observed at the channel/rib interface for a high compression ratio. To determine the mechanism of water transport in the GDL, a multiphase lattice Boltzmann method (LBM) is developed for a simplified porous structure of the GDL. The observation of lattice Boltzmann (LB) simulation shows that the compression ratio significantly affects the water transport in the GDL. The results indicate that the lower compression ratio reduces the water saturation in the GDL. The simulation and experimental result are similar.

Using a computational fluid dynamics technique, the flow characteristics and particle residence time in a Taylor reactor were studied. Since flow characteristics in a Taylor reactor are dependent on the operating conditions, effects of the inlet flow velocity and reactor rotational speed were investigated. In addition, the particle residence time of LiNiMnCoO2 (NMC), which is a cathode material in lithium-ion battery, is estimated in the Taylor vortex flow (TVF) region. Without considering the complex chemical reaction at the inlet, the effect of Taylor flow was studied. The results show that the particle residence time increases as the rotating speed increased and the flow rate decreased.

Using the multiphase lattice Boltzmann method (LBM), the electrolyte transport dynamics in the two-dimensional electrode structure of a lithium-ion battery are simulated. The effect of the compression ratio of a porous electrode on wettability is explored with respect to variations of porosity and particle shape. The electrolyte distribution in the electrode and the electrolyte saturation profile are examined in order to evaluate the wetting capability at various compression ratios. The results show that wettability in the electrode decreases as the compression ratio increases. In a highly compressed electrode, the through-plane permeation of liquid electrolyte is small. Thus, the electrolytes are mainly observed at the interface of the electrode and separator. The anode has lower wettability than the cathode due to the deformation of particle shape during the manufacturing process. Therefore, particle shape has a strong effect on wettability. The two-dimensional LBM approach used in this study characterizes the electrolyte transport phenomena inside the electrode and allows us to compare the wettability between the cathode and anode at various compression ratios.

The thermal behavior of pouch-type lithium-ion batteries during discharge and charge cycles is investigated by numerical simulation. A transient thermal model using finite element method software is developed through the modification of an electrochemical-thermal model. The developed model is validated with experimental data. For the experiment, a 304252 pouch cell is fabricated and tested in the laboratory. This model captures the dynamic responses of temperature, and distributions of current density and temperature, during discharge and charge cycles. Our results indicate that the discharge temperature is higher than the charge temperature at cut-off voltage. The temperature distribution upon discharge is similar to that of charge. On the other hand, different temperature distributions are observed at various C rates. The temperature profiles obtained from modeling and experiment are in good agreement.

전해액 포화도 ∆p : 압력차 t : 시간 : 속도V : 상호작용 포탠셜 w : 가중함수 그리스문자 µ : 점성계수 ν : 동점성계수 ρ : 밀도 τ : 완화시간 ψ : 밀도함수 첨자 e : 전해액 Key Words: Lattice Boltzmann Method(격자볼츠만법), Lithium Ion Battery(리튬이온전지), Electrolyte Wetting(전해액 함침), Electrode Compression(전극압축) 초록: 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 2차원 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. Abstract: 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.

The thermal behavior of lithium ion battery during charge and discharge is investigated by a numerical simulation. The commercially available cylindrical 18650 battery is modeled in this study. Two different models are used. The porous electrode model is simulated to obtain the Li content inside the particles. The transient thermo-electric model is used to predict the temperature distribution inside the cell. The results suggest that the increase in temperature during discharge is higher than that during charge. The temperature difference between charge and discharge is decreased with increasing C-rates. At a rate of 1C, the discharge temperature increases with a waving region at the beginning, whereas the charge temperature increases until certain point and then decreases. The thermal behavior is closely related to the change in entropy and applied current.

Three-dimensional comprehensive model of micro-scale transport in positive electrode/ electrolyte/negative electrode(PEN) and macro-scale transport in gas channel of anode supported SOFCs (solid oxide fuel cells) is developed in object-oriented CFD code Open Field Operation and Manipulation (OpenFOAM). The numerical procedure consists of calculations of complex phenomena which are fully coupled together with electrochemical reaction kinetics, mass balance, and energy balance, interacting between porous PEN structure and fluid gas channel. Computational fluid dynamics (CFD) was performed in flow channels with calculations of mass balance and continuum micro-scale model were used to predict the electrochemical characteristics in PEN. The distributions of current density and mass fraction are employed to suggest a dependency. To validate our numerical model, we compare the simulated results with experimental data at intermediate temperatures. This study provides detailed information of heat and mass transport phenomena with electro-chemical characteristics for intermediate temperature SOFCs. References [1] OpenFOAMⓇ, 2016, User and Programmer’s Guide, OpenCFD Ltd., available from http://www.openfoam.com.

Three-dimensional comprehensive model of micro-scale transport in PEN (positive electrode/ electrolyte/negative electrode) and macro-scale transport in gas channel of anode supported SOFCs (solid oxide fuel cells) is developed in object-oriented CFD code Open Field Operation and Manipulation (OpenFOAM). The numerical procedure consists of calculations of complex phenomena which are fully coupled together with electrochemical reaction kinetics, mass balance, and energy balance, interacting between porous PEN structure and fluid gas channel. The Computational fluid dynamics (CFD) was performed in flow channels with calculations of mass balance and continuum micro-scale model were used to predict the electrochemical characteristics in PEN. The temperature distributions, temperature profiles, and standard deviations are investigated at different average current densities to evaluate the uniformity. The distributions of current density and mass fraction are employed to suggest a dependency. This study provides detailed information of heat and mass transport phenomena with electro-chemical characteristics for intermediate temperature SOFCs

In this study, the effects of spacer and variation of spacer height in reverse electrodialysis (RED) on the seawater and ion transport were investigated. A three-dimensional computational fluid dynamics (CFD) simulation for a hexagonal spacer was constructed. The results showed that the swirl in the channel and ion transport rate to the membrane were enhanced at higher Reynolds number, on the other hand, pressure difference between the inlet and outlet was increased. Moreover thicker spacer increased Power number and Sherwood number.

The effect of rib on the dynamic behavior of liquid water transport in gas diffusion layer (GDL) is studied. The mechanism of water transport dynamics investigated using multiphase lattice Boltzmann method (LBM). Simulation with a simplified two-dimensional model is used to predict liquid water transport processes in local regions, instead of pursuing a three-dimensional numerical analysis for the entire domain. The observation of lattice Boltzmann (LB) simulation shows that the rib changes the water transport behavior and significantly affects the water transport in GDL.

The solid oxide fuel cell is an electro-chemical device which converts chemical energy into electricity and heat. To compete in today's market, design improvements, in terms of performance and life cycle, are required. Numerical prototypes can accelerate design and development progress. In this programme of research, a three- dimensional solid oxide fuel cell prototype, openFuelCell, based on open-source computational fluid dynamics software was developed and applied to a single cell. Transport phenomena, combined with the solution to the local Nernst equation for the open-circuit potential, as well as the Kirchhoff-Ohm relationship for the local current density, allow local electro-chemistry, fluid flow, multi-component species transport, and multi-region thermal analysis to be considered. The underlying physicochemical hydrodynamics, including porous- electrode and electro-chemical effects are described in detail. The openFuelCell program is developed in an object-oriented open- source C++ library. The code is available at http://openfuelcell.sourceforge.net/. The paper also describes domain decomposition techniques considered in the context of highly efficient parallel programming

This study numerically investigates pressure drop and flow distribution characteristics of serpentine flow fields (SFFs) that are designed for polymer electrolyte membrane fuel cells, which consider the Poiseuille flow with secondary pressure drop in the gas channel (GC) and the Darcy flow in the porous gas diffusion layer (GDL). The numerical results for a conventional SFF agreed well with those obtained via computational fluid dynamics simulations, thus proving the validity of the present flow network model. This model is employed to characterize various single and parallel SFFs, including multi-pass serpentine flow fields (MPSFFs). Findings reveal that under-rib convection (convective flow through GDL under an interconnector rib) is an important transport process for conventional SFFs, with its intensity being significantly enhanced as GDL permeability increases. The results also indicate that under-rib convection can be significantly improved by employing MPSFFs as the reactant flow field, because of the closely interlaced structure of GC regions that have different path-lengths from the inlet. However, reactant flow rate through GCs proportionally decreases as under-rib convection intensity increases, suggesting that proper optimization is required between the flow velocity in GCs and the under-rib convection intensity in GDLs.

A lab-scale proton exchange membrane fuel cell (PEMFC) is investigated at automotive operating condition. The comparison of straight-parallel PEMFC and serpentine PEMFC is carried out with detailed description of these flow-field configurations. A three-dimensional model is developed taking into account electrochemical reaction and evaporation/condensation of water which can affect on the overall flow field. The straight-parallel PEMFC has considerably low internal pressure drop which is beneficial to automotive application. Non-uniform temperature and current density distributions due to flow maldistribution are identified as a challenge to the straight-parallel PEMFC. To improve uniformity of these variables, we conducted an investigation on the manifold parameters. The result indicates that the wider manifold configuration has better cell performance as well as more uniform temperature and current density distributions than the narrower manifold configuration. This is primarily caused by improved uniformity on the flow velocity profile among parallel channels.

SUMMARY The effect of a cooling plate on a PEM fuel cell was studied by three-dimensional CFD modeling. The cyclic cell and the single cell were compared for the evaluation of the influence of cooling plate. The cyclic cell consisted of a single cell and a two-channel serpentine flow-field coolant, which then repeats by using a cyclic boundary on both ends. The single cell was composed of an active area of 200 cm2 and a 10-channel serpentine flow field. The following sets of equations were used in the model: the conservation of electrical current, the mass conservation of gases species, the Navier–Stokes equation, the energy balance, and the water phase change model. Comparison of cyclic cell and single cell shows that the voltage of cyclic cell was reduced at high current densities because of the increased ohmic losses. This was caused by the combined effect of membrane dehydration and higher local temperature. However, the cyclic cell showed more uniform current density distribution than the single cell, and this is attributed to the use of cooling plate. Increasing the coolant flux enhanced the cell performance by reducing the ohmic loss. Copyright © 2011 John Wiley & Sons, Ltd.

The effect of relative humidity of the cathode (RHC) on proton exchange membrane (PEM) fuel cells has been studied focusing on automotive operation. Computational fluid dynamics (CFD) simulations were performed on a 300-cm 2 serpentine flow-field configuration at various RHC levels. The dependency of current density, membrane water contents, net water flux on the performance and the uniformity was investigated. The uniformity of current density and temperature was evaluated by employing standard deviation. The water balance inside a fuel cell was examined by describing electro-osmotic drag and back diffusion. It was concluded that the RHC has strong effect on the cell performance and uniformity. The dry RHC showed low cell voltage and non-uniform distributions of current density and temperature, whereas high RHC presented increased cell performance and uniform distributions of current density and temperature with well-hydrated membrane electrode assembly (MEA). Also the local current density distribution was strongly dependent on the local membrane water contents distribution that has complex phenomena of water transport. The elimination of external humidifier is desirable for the automotive operation, but it could degrade cell performance and durability due to dehydration of the MEA. Therefore a proper humidification of the reactant is necessary.

Transient and thermo-electric finite element analysis (FEA) of cylindrical lithium ion (Li-ion) battery was presented. The simplified model by adopting a cylindrical coordinate was employed. This model provides the thermal behavior of Li-ion battery during discharge cycle. The mathematical model solves conservation of energy considering heat generations due to both joule heating and entropy change. A LiCoO 2 /C battery at various discharge rates was investigated. The temperature profile from simulation had similar tendency with experiment. The temperature profile was decomposed with contributions of each heat sources and was presented at several discharge rates. It was found that the contribution of heat source due to joule heating was significant at a high discharge rate, whereas that due to entropy change was dominant at a low discharge rate. Also the effect of cooling condition and the LiNiCoMnO 2 /C battery were analyzed for the purpose of temperature reduction.

A two-dimensional micro/macroscale model is proposed as an efficient numerical framework for simulating intermediate temperature solid oxide fuel cells (IT-SOFCs). This model employs a comprehensive microscale model that describes the detailed electrochemical reactions in Ni/YSZ cermet anodes and LSM/YSZ composite cathodes based on the three-phase boundary length (TPBL). A simplified macroscale model has been combined with the microscale model to consider the heat and mass transport processes in IT-SOFCs with prescribed fully-developed laminar velocity profiles in gas channels. A hydrogen-fed IT-SOFC is simulated at various operating conditions in order to demonstrate the capabilities of the proposed micro/macroscale model. The results elucidate the effects of co- and counter-flow configurations, inlet temperature, and air and fuel flow rates on the performance of the IT-SOFC.

The two-dimensional comprehensive CFD model of anode-supported SOFCs operating at intermediate temperature has been presented. This model provides transport phenomena of gas species with electrochemical characteristics and micro-structural properties, and predicts SOFC performance. The mathematical model solves conservation of electrons and ions, continuity equation, conservation of momentum, conservation of mass, and conservation of energy. A continuum micro-scale model based on statistical properties together with a mole-based conservation model was employed. CFD technique was used to solve the set of governing equations. The cell performance was decomposed with contributions of each overpotential and was presented at several operating temperatures with analysis of effective diffusivity. It was found that the contribution of potential gain due to temperature rising was considerably high. However it became non-significant at high operating temperature due to decreasing of effective diffusivity in AFL. These results showed that the performance and the distributions of current density, overpotentials, and mole fractions of gas species have a strong dependence upon temperature. From these results, it was concluded that the conservation of energy should be accommodated in comprehensive SOFC model. Also the useful information for the effect of parameters on cell performance and transport phenomena was provided.

A comprehensive model for detailed description of micro-scale transport and electro-chemical reaction in intermediate temperature SOFCs (solid oxide fuel cells) was developed by combining many relevant theoretical and experimental researches. Dependence of electro-chemical performance of PEN (positive electrode/electrolyte/negative electrode) on micro-structural parameters of electrodes was investigated through numerical simulation. Spatial distribution of transfer current density confirmed that TPBs (three phase boundaries) at electrode/electrolyte interface were most active for electro-chemical reaction and its contribution to overall reaction increased at higher current densities. Spatial gradient of total pressure in cathode was found to facilitate oxygen transport while that in anode hinder hydrogen transport. Among various micro-structural parameters for electrodes, particle diameter was found to be the most important one that governs the PEN performance; smaller particle diameter decreased activation overpotential with larger TPB length, while increasing mass transport resistance and concentration overpotential with smaller pore diameter. The proposed micro-model was found successful in micro-structural characterization of PEN performance, and thus believed to serve as a bridge connecting micro-scale models and macro-scale calculations.

The anodic performance enhancement of solid oxide fuel cells (SOFCs) by introducing penetrating electrolyte structures was investigated using a random resistor network model considering the transport of electrons and ions, and the electrochemical reaction in composite anodes. The composite anode was modeled as a mixture of ionic and electronic particles, randomly distributed at simple cubic lattice points. The dependence of the anodic polarization resistances on the volume fraction of the electronic phase, the thickness of the anode, and the insertion of various penetrating electrolyte structures were explored to obtain design criteria for best performing composite anodes. The network simulation showed that the penetrating electrolyte structures are advantageous over flat electrolytes by enabling more efficient use of electrochemical reaction sites, and thereby reducing the polarization resistances.

The water transport in a gas diffusion layer (GDL) has been investigated using two-dimensional lattice Boltzmann (LB) simulation. The LB model is developed to simulate the dynamic behavior of liquid water and enables to visualize the water-invasion process through micro-pores in GDL. To investigate the effect of rib structure on water invasion process in GDL, two different cases (i.e., with and without rib structure) are compared. The numerical model is verified by the comparison of the flow permeabilities in GDL. The validation result indicates that the LB model can properly predict the permeability of GDL and enables to simulate the water transport behavior in the GDL. The reconstruction of GDL is established by randomly placing the particles in GDL and ignoring the GDL deformation due to clamping force. The results of LB simulation confirm that the liquid water transport inside GDL is strongly governed by capillary force and the rib structure greatly impacts on the water transport behavior. The rib structure influences on the location of water breakthrough by comparing the simulation results of two different cases. This is due to the higher resistance force underneath the rib, resulting in the change of flow path which preferentially selects the lower resistance force. The water saturation level under the channel is higher than that under the rib caused by the suppression of growth of water cluster. After water breakthrough, the liquid water distribution under the channel has little change, whereas that under the rib keeps stretching for a while. The result indicates that a careful control of rib structure would enhance the water removal from the GDL. Therefore further studies for the optimum design of rib structure are needed. In an operating PEMFCs, the mechanism of water transport and wetting characteristics play an important role on flooding behavior. Therefore the results of the present study would contribute to the novel design for better water removal and flooding alleviation from the GDL.

In this work, aggregation and breakage of Li-ion precursor in Taylor-reactor are studied for various simulation condition, i.e., agitation rate, particle property, and reactor direction. The mean particle size and distribution is important to electrochemical performance of cathode materials. The population balance equation (PBE) is solved for coupling between particle interaction and fluid dynamic. The quadrature method of moments (QMOM) is implemented in a commercial computational fluid dynamics (CFD) code. Sum of three aggregation kernels, such as turbulent, Brownian, and Stokes aggregation, is considered for the calculation. [1] Breakage kernel is a combination of power-law kernel and various daughter distribution functions. Collision efficiency is assumed to be equal and the precursor is considered as spherical particle. Three-dimensional analysis is implemented and the simulation results are compared with experimental data. [1] L. Claudotte, N. Rimbert, P. Gardin, M. Simonnet, J. Lehmann, and B. Oesterle, AIChE J., Vol.56, No.9, pp. 2347-2355 (2010)

LBM for multi-phase fluid mixture is applied to the problem of electrolyte transport phenomena in two-dimensional porous electrode structure of LIBs. LB model successfully simulates the complicated microscopic behaviors of liquid electrolyte in porous electrode providing the mechanism of liquid electrolyte transport in LIBs. It is shown that LBM approach is an effective tool to investigate electrolyte transport phenomena in porous electrode with wettability taken into consideration. The results indicate that the wettability in porous electrode is strongly influenced by two-phase (electrolyte and air) transport and thus removal of existing air can be a bottleneck for the enhancement of wettability. Improving the wettability can be attained by controlling the material properties such as porosity, particle size and contact angle to assist in an efficient distribution of liquid electrolyte.

This study presents the effect of compression ratio on the dynamic behavior of liquid water transport in GDL. The experimental study investigates the emergence and growth of liquid droplet in the channel at various compression ratios by adopting direct visualization device. The results of the experiment show that water breakthrough occurs at the channel for low compression ratio, whereas it is observed at the channel/rib interface for high compression ratio. To determine the mechanism of water transport dynamics in GDL, multiphase lattice Boltzmann method (LBM) is developed with simplified porous structure of GDL. The observation of LB simulation shows that the compression ratio significantly affects the water transport in GDL. The results indicate that the lower compression ratio is favorable for the fuel cell performance by reducing the water saturation in GDL. Both simulation and experiment present similar result.

Taylor reactor is composed of two co-axial cylinders where the outer one is stationary and the inner one is rotating. Recently, Taylor reactor is applied on the lithium ion battery to produce cathode material. In the reactor, complex chemical reactions and particle growth occur. The particle size and distribution have significant impact on the performance of cathode material. This study simulates inter-particle aggregation and breakage in Taylor reactor and predicts particle size and distribution. The simulated results are compared with experiment. The quadrature method of moments (QMOM) is implemented to solve a population balance equation (PBE). For the aggregation kernel, the sum of turbulence kernel and Brownian aggregation kernel is considered. The power-law kernel is taken as a breakage kernel. The mixture model is used to describe the interaction between continuous phase and dispersed phase. The effect of internal flow on the dispersed phase (i.e. particle) is investigated by changing rpm.

Li(Ni0.6Mn0.2Co0.2)O2 (NMC622) cathode materials have been recognized as the next generation cathode materials due to its higher capacity and lower raw material cost than commercialized cathode materials such as NMC532. Thus, many industrial companies have been made every effort to commercialize and apply the NMC622 to lithium ion battery system such as energy storage system (ESS). However, production cost of NMC622 still has been recognized as expensive material to be applied in the industrial field and it becomes main issues to be overcome. CSTR (Continuous Stirred Tank Reactor) has been widely applied in the industrial field to produce the NMC622 precursor but it has initial long stabilization time as well as low production efficiency. This is caused by the original limitation of CSTR such as the low mass transfer rate and required complete mixing zone to stabilize the system. Thus, in this study, we suggest the novel reactor system that shows the higher mass transfer rate as well as higher production rate than those of CSTR. Developed novel reactor system uses the taylor-couette flows to induce higher mass transfer rate and production efficiency with uniform particle size distribution. In this study, we synthesized NMC622 using taylor-couette reactor to understand the function and mechanism of the operation. The effect of operating parameters, i.e. pH, operating rpm, and feed retention time, in the taylor-couette reactor, was investigated thoroughly to evaluate the feasibility to produce NMC622 precursor. Produced precursors are characterized using SEM, XRD, ICP, FIB, PSA. Then, cathode materials are prepared and tested using a galvanostatic intermittent titration method (GITT) to understand the electrochemical properties. This study verified that taylor couette reactor is feasible process to be applied to the commercial NMC622 production. Acknowledgement - This work was supported by the Korea Institute of Energy Technology Evaluation and Planning under the Energy Technology Development Program (20132020101750)

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