Computational study of the transport mechanisms of molecules and ions in solid materials

Transport of ions and molecules in solids is a very important process in many technological applications, for example, in drug delivery, separation processes, and in power sources such as ion diffusion in electrodes or in solid electrolytes. Progress in the understanding of the ionic and molecular transport mechanisms in solids can be used to substantially increase the performance of devices. In this dissertation we use ab initio calculations and molecular dynamics simulations to investigate the mechamisn of transport in solid. We first analyze molecular transport and storage of H2. Different lightweight carbon materials have been of great interest for H2 storage. However, pure carbon materials have low H2 storage capacity at ambient conditions and cannot satisfy current required storage capacities. Modification of carbon materials that enhance the interaction between H2 and absorbents and thus improve the physisorption of H2, is needed for hydrogen storage. In this dissertation, corannulene and alkali metal-doped corannulene are investigated as candidate materials for hydrogen storage. Molecularalso investigated. Using computational chemistry, we predict enhanced H2 adsorption on molecular systems with modification and hydrogen uptake can reach DOE target of 6.5wt% at at 294 bar at 273 K, and 309 bar at 300 K. In the second part of this dissertation, we study the lithium ion transport from a solid electrolyte phase to a solid electrode phase. Improvement of ionic transport in solid electrolytes is a key element in the development of the solid lithium ion batteries. One promising material is dilithium phthalocyanine (Li2Pc), which upon self-assembly may form conducting channels for fast ion transport. Computational chemistry is employed to investigate such phenomena: (1) to analyze the crystalline structure of Li2Pc and formation of conducting channels; (2) to understand the transport of Li ions inside channels driven by an electric field; (3) to study the continuity of the conducting channels through interface. The study shows Li2Pc has higher conductivity than PEO as electrolyte.