Our mission is to develop an understanding of (i) structure-property relationships, (ii) transport mechanisms, (iii) interfacial electrode-electrolyte structure and its evolution, and (iv) electron and ion transfer reactions in deep eutectic solvents (DES) and soft nanoparticles (SNP), and (v) how these structures and properties can be tailored at the atomistic level to advance electrochemical performance in electrochemical energy storage systems. To use know-how gained through synergizing experimental and theoretical investigations to enable design and synthesis of new, safe, and high energy and power density electrolytes that will enable next-generation energy storage systems.

BEES Research Impacts Many Fields.

Motivation

Discovery of new electrolytes is needed for advancing the fundamental science and enabling new opportunities in electrochemical systems including redox flow batteries, electrochemical capacitors, electrocatalysis, electrodeposition, separations and sensors. Specifically, by designing new electrolytes with higher concentrations of electrochemically active species, lack of flammability and ease of control over transport properties, substantial improvements will be realized in (i) energy and power density, (ii) safety and reductions in environmental impact, and (iii) cost of energy storage systems. BEES EFRC sets out a comprehensive research program that leverages expertise in the theory-guided synthesis and characterization synergizing simulations and experiments.

BEES Research Enables Next Generation Energy Storage Systems.

Strategy

BEES researchers in collaborative multidisciplinary teams employ electroanalytical techniques, spectroscopy, synchrotron based X-ray and neutron techniques, as well as advanced computational methods to probe fundamental properties and interfacial chemistry of two material approaches denoted as thrusts. The two research thrusts within BEES are: (1) Deep Eutectic Solvents and (2) Soft Nanoparticles.

Thrust 1: DES

Deep Eutectic Solvents are a class of liquids comprised generally of a hydrogen bond donor and a hydrogen bond acceptor. DES are non-toxic, biodegradable, stable, nonvolatile, and nonflammable. They have a high degree of structural flexibility. DES enable electrochemical reactions without the constraints of aqueous solvents. The strategy of Thrust 1 is to unravel the fundamental underpinnings of the relationship between the composition and structure that determine the physicochemical and electrochemical properties of DES so that new DES functionalized with redox active groups can be developed as new electrolyte systems, improving redox-active material solubility and facilitating fast interfacial electron transfer reactions. The main approach of Thrust 1 hypothesizes that spatial and dynamic heterogeneity introduced by noncovalent interactions alters the molecular energy landscape and leads to mesoscale organization and dynamics that determine the macroscopic properties of DES. The outcome of studies probing this hypothesis will be the basis for (i) tailoring DES structures for specific electrochemical and transport properties, and (ii) extending the electrochemical stability of the DES structures over wide potential windows to enable new electrochemical reactions not feasible in traditional DES systems. We will verify the developed structure-property relations by performing electrochemical studies on the electron and charge transfer reactions.

Thrust 2: SNP

Soft Nanoparticle electrolytes are heterogeneous, multiphase systems where liquid droplets are dispersed in a carrier phase. An example of a SNP electrolyte is a nano-emulsion in which droplets containing electroactive species are surrounded by a fluid that provides conductivity. Another example is a NOHM (Nanoparticle Organic Hybrid Materials) which are liquids formed from hard nanoparticles with attached, possibly functionalized, polymeric chains. The approach of Thrust 2 is to establish unique paths for decoupling the nature and solubility of electroactive material from the conductivity and transport of ions in the surrounding solution, which may be an aqueous phase or a non-aqueous phase. The guiding hypotheses for Thrust 2 are (i) that microemulsions and NOHMs can controllably take up and release redox active species and (ii) that SNP-contained redox active species can be converted through direct or mediated electron transfer across the boundaries of the SNP. The outcome of studies probing this hypothesis will be the basis to tailor structures for specific electrochemical and transport properties as well as for the uptake of electroactive species and to develop the electrochemical science using SNP.