(6if) Multi-Scale Modeling to Study Soft Matter

Rajput, N. N. - Presenter, Lawrence Berkeley National Laboratory

Molecular simulations are indispensible tools to capture molecular level properties of bulk solutions as well as interfaces. My goal is to couple Quantum mechanical (QM) calculations with molecular dynamics (MD) to understand the electronic structure, energies as well as bulk structural and dynamical properties of soft matter. QM calculations are well suited to study accurate energies, forces and reaction chemistry. On the other hand, MD simulations are capable to study many body properties of thousands of molecules at longer time scale, which is essential to capture realistic properties of bulk solutions as well as interfaces. ILs have gained immense attention recently due to great thermal, chemical, and electrochemical stability and their non-volatile and non-explosive nature. Because of their numerous applications and unique properties, there is a rapidly growing scientific and commercial interest in ILs. In particular, some experimental studies have shown their use as potential electrolytes for batteries. I plan to study electrolytes doped ILs for multivalent batteries using QM and MD simulations. The current state-of-art Lithium ion batteries are suffering with their limited performance, short lifetime and safety concerns. An approach to achieve energy density higher than the existing Li-ion batteries is to replace monovalent Li-ion by multivalent ions such as Mg2+, Ca2+, Zn2+ and Al3+.1,2 Using QM calculations we can study the electrochemical stability window, bond dissociation energy and dissociation constant of ion pairs. The optimized structure and electrostatic potential from QM calculations can be used to generate force filed parameters for MD simulations. MD simulations can then be used to predict solvation structure, diffusion coefficient and viscosity of electrolytes. It is important to understand the cation-anion distribution, bonding structure and ion exchange mechanism in these solutions. The effect of temperature and concentration will be considered on these properties. Interfacial properties play important role in determining performance of electrochemical devices and it is hard to study interfaces experiments. In the next step these properties will be studied at the electrode/electrolyte interface. Significant information about the interfaces can be obtained by studying solvation structure, charge transfer and dynamical properties of electrolytes at the electrode/electrolyte interface. Molecular simulations will be the key for studying the molecular level properties of IL doped electrolytes at the interface leading to advancement in designing tomorrow’s high performance electrochemical devices

            (1)       Rajput, N. N.; Qu, X.; Sa, N.; Burrell, A. K.; Persson, K. A. Journal of the American Chemical Society 2015.

            (2)       Lin, M.-C.; Gong, M.; Lu, B.; Wu, Y.; Wang, D.-Y.; Guan, M.; Angell, M.; Chen, C.; Yang, J.; Hwang, B.-J.; Dai, H. Nature 2015, 520, 324.