Morphology and Mobility in Semi-Crystalline and Nanofilled Solid Polymer Electrolytes

TECHNICAL SUMMARY: This project addresses solid polymer electrolytes [SPEs], a class of materials with the potential for use in lithium ion batteries. The specific aims are to produce nanocomposites with controllable particle dispersion, determine the nanoscale morphology of coexisting crystalline phases, and determine the relationship between polymer dynamics and increased conductivity. Nanocomposites are relevant to SPEs because they have been demonstrated to increase conductivity into the practical range. However, the mechanism by which nanoparticles increase conductivity in SPEs is not well understood. One of the problems is aggregation of the particles, which is significant using standard preparation methods and leads to irreproducible samples and results. The project will apply a technique recently reported for controlling the length scale of phase separation in a polymer blend. This technique encapsulates the polymers in a nano-emulsion, followed by evaporation of the polymer phase solvent, leaving a polymer nano-sphere with controllable size suspended in a non-solvent by use of a surfactant. Two such preparations are mixed to form the blend. The current project will replace one of the polymers with a nanoparticle, but otherwise follow the same procedure. Production of nanocomposites with well controlled spacing will allow for study of crystallization, polymer mobility and conductivity under reproducible conditions, thus providing a mechanism for enhanced conductivity, as well as fundamental understanding of the behavior of confined polymer/salt complexes.

NON-TECHNICAL SUMMARY: This project seeks to improve the properties of a material with potential use as a flexible and lightweight battery in portable and other devices. The required material is a solid plastic, and its use in batteries improves with the addition of nanometer-sized particles. The reason the particles improve properties is not well understood, because dispersion of the particles in the plastic matrix is difficult. The project will use a new method for dispersion of the particles, producing well characterized materials that can be used to gain the needed understanding. The materials will be studied using neutron scattering, a technique measuring both existence and movement of structures over nanometer length scales. The US has recently invested significantly in neutron scattering facilities: for example the Spallation Neutron Source at Oakridge National Laboratories. These expanded facilities require additional investigators to use the instruments. Thus outreach activities targeted towards scientific areas where neutron scattering is under-utilized is a part of this project.