Dendrite initiation and growth in lithium/polymer systems

In this work, we develop models to describe dendrite initiation and growth in rechargeable battery systems with lithium anodes. The first chapter introduces the general experimental setup that is typically employed in the laboratory to characterize electrolytic solution transport and the kinetics of lithium electrodes. The second and third chapters outline transport and kinetic models applicable to lithium/polymer battery systems. First, a general transport model for binary electrolytic solutions is derived; this development allows the coupling between mass and momentum transport in the electrolytic solution to be taken into account and ties the binary interaction parameters familiar from the Stefan-Maxwell theory of diffusion to properties measured in typical electrolytic-solution characterization studies. Then, the lithium/solution interface is treated. A simplified model of the interface is introduced, and experimental values of the kinetic parameters for several relevant lithium/polymer systems are presented.; Mullins-Sekerka linear stability analysis and the Barton-Bockris dendrite propagation model are popular methods used to describe cathodic roughening and dendritic growth. These commonly cited theories employ kinetic relationships that differ in mathematical form, but both contain the effects of surface tension and local concentration deviations induced by surface roughening. In chapter 4, a kinetic model is developed that additionally includes mechanical forces such as elasticity, viscous drag, and pressure, showing their effect on exchange current densities and potentials at roughening interfaces. The proposed kinetic expression describes the current density in terms of applied overpotential at deformed interfaces with arbitrary three-dimensional interfacial geometry.; Dendrite propagation in a parallel-electrode lithium/polymer cell during galvanostatic charging has been modeled in chapter 5. The growth model is surface-energy controlled, incorporating the effect of dendrite tip curvature into the dendrite growth kinetics. Using data representative of a typical lithium/liquid polymer system, it is shown that dendrites accelerate across cells under all conditions, and that propagation can always be slowed by lowering the current density. Cell shorting is found to occur during typical charges at current densities above 75% of the limiting current. Increased interelectrode distance slows failure, but the advantages are revealed to decrease as distance increases.; Chapter 6 treats interfacial stability in lithium/polymer systems where the electrolyte is solid. (Abstract shortened by UMI.)...