Engineering topics
Lueth, Christopher
Publications and source records attributed to Lueth, Christopher.
Effects of morphology on ion transport in ionomers for energy storage
Polymer electrolytes are essential elements of current and next-generation energy storage applications. An important class of polymer electrolytes is ionomers, in which one of the ions is covalently bound to the polymer backbone. Ionomers are currently used in fuel cells, and show extraordinary promise as solid electrolytes in batteries for transportation and portable power applications. Solid electrolytes are desirable for a variety of reasons. A primary one is safety: the lack of solvent leads to fewer electrochemical reactions (e.g. with the electrodes) and the absence of flammable liquids. Solvent-free electrolytes allow for less packaging (and hence higher energy density batteries) and easier manufacture. Single-ion conductors such as ionomers also have the advantage of higher efficiency (high lithium transference numbers), since the anions are bound to the polymer backbone and the current is primarily due to the cations that actively participate in the electrochemical reactions. However, to date ionomeric materials do not have sufficiently high conductivities. Ion transport mechanisms in ionomers and their relation to molecular structure are poorly understood, although it is known that ion transport is coupled to polymeric motion and to the nanoscale morphology of ionic aggregates that often self-assemble in the polymer matrix. In this project we investigate the morphol ogy and ion dynamics in ionomer melts using ab initio calculations, NMR experiments, and both atomistic and coarse-grained molecular dynamics simulations. We find that the aggre gate morphology depends strongly on polymer architecture, neutralizing cation, and degree of neutralization. This morphology in turn affects the counterion dynamics; we find that counte rions diffuse more quickly in systems with percolated aggregates than in systems with discrete aggregates.
Predicting Electrochemical Phenomena in Lithium Molten Salt Thermal Batteries.
Abstract not provided.
CanTrilBat
This application can determine the performance and chemical behavior of batteries in 1D when they are cycled. With CanTrilBat, we are developing predictive phenomenological models for battery systems to predict operating performance and rate limiting steps in the performance of battery models. Particular attention is paid to primary and secondary chemistry mechanisms, such as the thermal runaway mechanisms experienced in secondary lithium ion batteries or self-discharge reaction mechanism that all batteries experience to one extent or another. The first application of this model has been for modeling the performance of thermal batteries. However, an implementation for secondary ion batteries is next. CanTrilBat applications solves transient problems involving batteries. It is a 1-D application that represents 3-D physical systems that can be reduced using the porous flow approximation for the anode, cathode, and separator. A control volume formulation is used to track conserved quantities. An operator-split approach is used to calculate the chemistry, diffusion and electronic transport that occurs within cathode and anode particles, allowing for the reduction in code complexity.