Conducting (suspension) flowable electrodes for water and energy technologies

Abstract

This thesis focuses on the development a new family of flowable electrochemical systems based on suspension electrodes to address key critical infrastructures needs: grid energy storage and water deionization. The research herein combines classical aspects of electrochemistry, colloidal science, material science, and rheology to describe ion and charge percolation processes in suspension electrodes. A suspension electrodes is an example of a new and emerging multiphase material comprised of an active material suspended in electrolytic medium. Gravimetrically the electrolyte is the majority component and aids in physical transport of the active (charge-storing) material. By continuously replenishing the electroactive region with uncharged material, suspension electrodes allow for continuous charge storage. This enables scalability of solid-state energy storage systems (supercapacitors and batteries). Ultimately, this dissertation outlines the fundamental and underlying electrochemical, kinetic, and rheological properties of suspension electrodes. Carbon-based and inorganic (manganese oxide) materials are studied as the active material in a suspension electrode. The compositional loading and the material properties (conductivity, porosity, texture) are identified and studied for their affects on charge storage and rheological properties in a suspension electrode. With an ultimate goal of achieving high energy density, opportunities for pseudocapacitive suspension electrodes via the addition of soluble organic molecules and redox-metal ions are examined (faradic processes). The role of carbon surface heteroatoms on the combined rheological, electrochemical, and deionizing properties of capacitive suspension electrodes for desalination is studied. High mass loaded suspension electrodes (28 wt% carbon content) based on oxidized activated carbon displayed similar viscosities to lower mass loaded suspension electrodes (20 wt% carbon content) based on non-oxidized activated carbon. This work provides a holistic examination of suspension electrodes and reports key nanoscale material properties and how these properties transition to system level ion removal and charge storage properties.%%%%Ph.D., Materials Science and Engineering – Drexel University, 2015