Our group conducts both experimental and theoretical research on complex electrochemical systems. An integrated research methodology coupling electrochemical characterization and modeling methods is employed to study the fundamental principles in electrochemical technologies. We aim to characterize the transport phenomena and reaction mechanisms in complex electrochemical systems as described below in details.
1) Critical Link between Cell Design and Battery Performance in Lithium-Sulfur Batteries
Li-S batteries have gained significant attention as a promising candidate for energy storage systems beyond Li-ion batteries due to their high theoretical specific energy of 2567 Wh/kg. In addition, sulfur is naturally abundant, non-toxic, and inexpensive. Li-S batteries typically contain a Li metal anode, a porous separator, and a sulfur-carbon porous cathode filled with an organic electrolyte. The overall reaction for the Li-S battery is 16Li + S8 → 8Li2S with a standard potential of U0 = 2.2 V (vs Li/Li+). Although Li-S batteries are highly attractive, they suffer from major challenges, which lead to rapid capacity fading and limitations in cycle life. Consequently, for the commercial use of the Li-S battery, its cycle life and energy density must be improved. Mathematical modeling coupled with electrochemical characterization is essential to have a better understanding of the reaction and degradation mechanisms in these batteries. These complex mechanisms in a Li-S cell that define the electrochemical performance of the battery, depends significantly on the electrode-level design parameters. Therefore, the link between the critical parameters at the materials-, cell- and systems-level in a Li-S battery should be examined; understanding the connection between the reaction and degradation mechanisms and key cell-level design parameters that define the battery performance is crucial to achieve the requirements for high energy density Li-S batteries. In our research group, we couple electrochemical characterization (ie. electrochemical impedance spectroscopy, galvanostatic cycling) and modeling (ie. electrochemical modeling, cell- and system-level performance modeling) methods to investigate this critical link between cell design and Li-S battery performance.
2) Electrodeposition of Metals and Metal/Ceramic Nanocomposites
The second research interest we have is the electrodeposition of metals and metal/ceramic nanocomposites. Chromium and cadmium containing coatings that are commonly used in the aerospace industry for wear and corrosion resistance will be replaced in the next decade due to environmental considerations. Nickel/ceramic particle nanocomposites have recently gained significant attention as wear-resistant coatings due to their high hardness and wear and corrosion resistances. Electrodeposition is advantageous for the production of these composites since it requires low operating temperature and cost and offers good control of the composite properties. The amount and uniformity of the ceramic particles in the deposit is critical to obtain superior mechanical and tribological composite properties. High and uniform particle incorporation into the deposit depends significantly on both the dispersion of the ceramic particles in the electrolyte and the electrodeposition parameters. Dispersants prevent the agglomeration of the ceramic particles in the electrolyte resulting in higher and more uniform particle incorporation into the deposit. However, dispersants may also adversely affect the electrodeposition kinetics while enhancing the stability of the nanoparticles in the electrolyte. Therefore, the major concern in the electrolyte design is achieving the optimum electrolyte concentration of the dispersant resulting in good particle stability in the electrolyte and thus high and uniform particle incorporation into the deposit without suppressing the electrodeposition. To obtain such a system, electrodeposition should be investigated in terms of nanoparticle dispersion in the electrolyte, electrodeposition kinetics, and nanoparticle amount in the deposit. In our lab, we use this integrated research methodology to investigate the electrodeposition of Ni/SiC, Ni/TiC and Ni/WC nanocomposites.
TUBITAK 3501 Career Grant No: 116M574
TUBITAK 2232 Reintegration Fellowship Grant No: 116C005
ENDAM, Center for Energy Materials and Storage Devices funded by the Turkey Ministry of Development Grant No: BAP-2016K121510
Bogazici University Start-Up Project No: 14443SUP
Middle East Technical University Research Project No: BAP-08-11-2016-049