An integrated study of ion dynamics and population distributions to understand the molecular underpinnings of charge transport through self-assembled solid polymer electrolytes

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The widespread adoption of intermittent renewable-produced electricity and electric vehicles can be accelerated by access to reliable lithium-based energy storage. Disruptive advances in these technologies face challenges stemming from fundamental knowledge gaps that limit power density and durability in the batteries. Both performance attributes are impacted by the nature of charge transport within solid-like ionic conductors that would be used in these batteries. A better understanding of these processes will benefit a wide range of technologically and commercially promising areas beyond sustainable electrical grid load-balancing and transportation. Specific additional examples include deployable sensors, gas separation, actuators, ion exchange membranes, and optoelectronic devices. This study will focus on understanding the fundamental aspects of ion diffusion through nanostructured polymeric matrices, and on using these insights to guide the design of solid polymer electrolytes for high power density lithium-ion batteries. As part of education outreach activities, the Principle Investigators will participate in the Academic Clark Excellence, program, ACE. This effort focuses on preparing and mentoring entering first-year students, especially those underrepresented in STEM, so that they can take full advantage of the research opportunities available in the sciences and can successfully fulfill the requirements of today's science careers or post-graduate studies in chemistry. The PIs have structured a series of activities and practices seeking to guide and mentor graduate students on job-seeking best practices, intellectual property law, and scientific writing.The goal of this project is to examine the lithium-ion (Li+) dynamics and population distribution within nanostructured polymeric ionic conductors to understand the mechanisms controlling charge transport through matrices with solid-like mechanical properties and liquid-like ion diffusion. The two-dimensional nuclear magnetic resonance (NMR) relaxation correlation experiments of the project are used to study a wide variety of ion conductors in an effort to achieve a more complete understanding of the dynamic processes controlling ion diffusion through polymers. This research plan aims to use lithium-conducting, poly(ethylene-imine)-based, diblock copolymers as a model system to study ion transport through mechanically robust membranes containing "ion-permeable", yet mechanically reinforcing, domains. Since the dynamics of most ion conducting processes through polymer matrices are governed by the same fundamental principles, the results of this work will impact the design of a wide variety of ion-transporting media. This research plan will quantify the effect of polymer backbone structure and dielectric constant on the effective concentration of charge carriers and their mobility through a nanostructured polymeric matrix. The target copolymers will serve as model compounds for fundamental phase behavior ion-bearing diblock copolymers. The structure-property relationships derived from this study will help guide the design of new ion conducting components for a variety of applications, such as lithium-ion batteries, water-free polymer electrolyte membrane fuel cells (PEMFC), non-aqueous redox flow batteries, dye sensitized solar cells, as examples.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.