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( Appiah Williams Agyei ),박주남,변승우,유명현,이용민 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
Li-ion batteries (LIB) as an energy storage device have been established as a leading and a promising candidate for automotive and aerospace applications. However, to meet the various application requirements, the energy and power density of LIBs need to be optimized for a given electrode material by controlling its porosity and thickness. Hence, we employ a mathematical model to study and optimize the electrochemical performance of Graphite/ LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> LIB cells with different cathode thicknesses and porosities. Ragone plots are generated for the various cell design. The LIB cells are optimized for discharge times ranging from 10 h to 2 min in order to map the maximum performance of this electrode chemistry under wide operating range. The study allows us to ascertain the ability of this chemistry to be used in a particular application.
( Williams Agyei Appiah ),박주남,변승우,유명현,이용민 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
To meet the various application requirements of LIBs, the energy and power density of LIBs needs to be optimized for a given electrode material by controlling its porosity and thickness. Changes in electrode thickness and porosity affect the electrochemical performance of LIBs. Hence we employ a mathematical model to study and optimize the electrochemical performance of graphite/LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> cells with different cathode thicknesses and porosities. A non-linear least square method is used to provide a better understanding of the different porosities and thicknesses on Li-ion transport in both liquid and solid phases. Ragone plots are generated for the various cell designs where the specific energy and average specific power are evaluated. The cells are optimized for discharge times ranging from 10 h to 2 min in order to map the maximum performance of this chemistry under wide operating range.
( Williams Agyei Appiah ),박주남,변승우,유명현,이용민 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
To quantify the capacity fade mechanism in lithium ion batteries composed of a spinel-based cathode and an artificial graphite, a comprehensive mathematical model describing the cycling performance of LiMn<sub>2</sub>O<sub>4</sub>/graphite lithium ion cell is developed in this work. The developed model is incorporated into the Newman’s Porous Composite Electrode framework (PCE) and implemented in the battery module of COMSOL Multiphysics. The proposed model is used to investigate the effects of variations in the ambient temperature and of voltage range of cycling on the capacity fade. The effect of changes in the volume fraction of cathode active material, resistance in the cell and state of charge are also studied.
Synergetic effects of blended cathode active materials: Simulation and Experiment
( Williams Agyei Appiah ),박주남,변승우,유명현,이용민 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
In the quest to achieve a higher capacity electrode materials for lithium ion batteries, different active materials for both cathode and anode are being studied. However, the available electrode materials which have been discovered have both good and bad sides. Hence, the electrochemical characteristics of Li-ion cells made of blended cathode material composed of LiMn2O4 and LiNi0.6Co0.2Mn0.2O2 and an artificial graphite anode are being studied via both experiments and simulation. The cycle performance of the two pure cell chemistries we modelled by considering Mn2+ dissolution in the cathode and solid electrolyte interphase information in the anode. By fitting our model predictions to the experimental data, the percentage of each contributing factor to the total capacity fade was determined. Ragone plots were used to study the correlation between the energy density and average specific power of the two pure chemistries and their blends.
2P-393 Computational analysis of capacity fade in spinel-based cathode and artificial graphite anode
( Williams Agyei Appiah ),박주남,변승우,유명현,이용민 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
A comprehensive mathematical model is developed to study the cycling performance of LiMn2O4/graphite lithium ion cells. The proposed model takes into consideration the formation and dissolution of the solid electrolyte interphase (SEI) at the anode, Mn(II) dissolution of LiMn2O4 cathode active material due to Mn(III) disproportionation reaction and its effects on the SEI at the anode as well as the formation of cathode electrolyte interphase (CEI) on the cathode. The developed model is incorporated into the Newman’s Porous Composite Electrode framework (PCE) and implemented in the battery module of COMSOL Multiphysics. The proposed model is used to study the effects of variations in temperature and voltage range of cycling on the capacity fade and changes in volume fraction of cathode active material, resistance in the cell and SEI thickness.
Appiah, Williams Agyei,Park, Joonam,Byun, Seoungwoo,Cho, Inseong,Mozer, Attila,Ryou, Myung-Hyun,Lee, Yong Min Elsevier 2018 Journal of Power Sources Vol.407 No.-
<P><B>Abstract</B></P> <P>A coupled chemo-mechanical model which considers the contact resistance as well as the influence of the attractive forces inside the contact area between the electrode and current collector was developed to evaluate the effects of the adhesive strength of a binding material on the electrochemical performance of silicon-based lithium-ion batteries. The increase in contact resistance between the electrode and current collector was introduced as a factor that reduces the electrochemical performance of the cell. The model predictions were validated with experimental data from coin-type half-cells composed of Li metal, Si electrodes, and Cu current collectors coated with binding materials with different adhesive strengths. The contact resistance increased with an increasing number of cyclic current rate. The adhesive strength decreased with cyclic current rate. The proposed model was used to investigate the effects of adhesive strength and various cell design parameters on the specific capacity of the Si-based Li-ion cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A coupled chemo-mechanical model for Si-based secondary batteries. </LI> <LI> Model parameterization and model validation. </LI> <LI> Contact resistance and adhesive strength between Si composite electrode and Cu current. </LI> <LI> Optimal electrode design for specific capacities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Appiah Williams Agyei ),박주남,변승우,유명현,이용민 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
To fully understand the capacity fade mechanism in lithium ion batteries composed of a spinel-based cathode and an artificial graphite, a comprehensive mathematical model describing the cycling performance of LiMn<sub>2</sub>O<sub>4</sub>/graphite lithium ion cell is developed in this work. The developed model is incorporated into the Newman`s Porous Composite Electrode framework (PCE) and implemented in the battery module of COMSOL Multiphysics. The proposed model is used to investigate the effects of variations in the ambient temperature and of voltage range of cycling on the capacity fade. The effect of changes in the volume fraction of cathode active material, resistance in the cell and state of charge are also studied.
( Williams Agyei Appiah ),박주남,변승우,유명현,이용민 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
To quantify the capacity fade mechanism in lithium ion batteries composed of a spinel-based cathode and an artificial graphite, a comprehensive mathematical model describing the cycling performance of LiMn2O4/graphite lithium ion cell is developed in this work. The developed model is incorporated into the Newman’s Porous Composite Electrode framework (PCE) and implemented in the battery module of COMSOL Multiphysics. The proposed model is used to investigate the effects of variations in the ambient temperature and of voltage range of cycling on the capacity fade. The effect of changes in the volume fraction of cathode active material, resistance in the cell and state of charge are also studied.
Appiah, Williams Agyei,Ryou, Myung-Hyun,Lee, Yong Min The Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.3
<P>The capacity fading behavior of a LiMn<SUB>2</SUB>O<SUB>4</SUB>/graphite lithium ion cells at different temperatures is analyzed using a physics-based porous composite electrode model and a parameter estimation technique. The parameter estimation technique is used to extract capacity fade dependent model parameters from experimental cycling data. Although the capacity fading mechanism of the LiMn<SUB>2</SUB>O<SUB>4</SUB>/graphite lithium ion cells are greatly influenced by temperature, major capacity fading mechanism is closely related to the trapping of Li ions into solid electrolyte interphase on the graphite negative electrode and the reduction in the volume fraction of the active material in the LiMn<SUB>2</SUB>O<SUB>4</SUB> positive electrode. At 25°C, the dominant capacity fading mechanisms is the formation of the solid electrolyte interphase while at 60°C the dominant capacity fading mechanism is the reduction in the volume fraction of the positive active material. The efficacy of the physics-based composite electrode model is validated with experimental discharge profiles obtained from cells cycled at 25 and 60°C.</P>