Optimizing Ion Mobility, Chemical Stability, and Mechanical Rigidity in Composite Electrolytes

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NON-TECHNICAL DESCRIPTION: Energy storage is a critical aspect of sustainable and renewable energy technologies, and mobile information systems. While the chemical nature of anode and cathode determines the amount of energy that can be stored in a battery of a given size, the separator material (or electrolyte) controls its charge cycling rates, lifetime, and structural integrity. High conductance of the ion responsible for the electrochemical conversion (e.g., lithium) facilitates high power release and short recharge times. Chemical compatibility between electrolyte and electrode materials prevents the formation of blocking layers that would suppress the electrochemical process. Mechanical rigidity of the electrolyte inhibits dendrite growth that can short circuit the device and lead to catastrophic failure (e.g., spontaneous combustion). Unfortunately, these performance criteria rely on conflicting materials properties, and the challenge lies in devising a composite structure that maximizes all these attributes. In this research, a combination of simulation-based predictive design, advanced materials synthesis approaches, microstructural characterization, and performance monitoring is employed to develop new composite electrolytes with unsurpassed performance. This project contributes to the development of human resources in an innovative way by training a doctoral student in combining experimental and computational tools of investigation, and providing research experiences for undergraduate students. Connections with secondary school educators are reached through an ASM High School Teachers Camp. As well, they are pursuing a new masters mentoring program for students from minority serving institutions. It is expected to have a dual benefit - on one hand, students are gaining insight into scientific research, and on the other hand, faculty are better-positioned to proactively recruit underrepresented minorities and women into doctoral programs in science and engineering.TECHNICAL DETAILS: The objective of this research is to develop composite battery electrolytes that exhibit high Li+ conductivity, that are mechanically rigid enough to suppress lithium dendrite growth and safely separate electrodes in self-supporting device structures, and that possess an electrochemical stability range wide enough to accommodate large electrode potential differences. While high ionic conductivity and transference numbers are important for the charge-discharge rates of batteries, stiffness and electrochemical stability are essential for taking advantage of the full redox potential of Li metal, and thus increase the gravimetric capacity of energy storage for these devices. A combination of molecular simulation-based predictive design, hybrid organic-inorganic sol-gel synthesis, in situ monitoring of microstructural developments using inelastic light scattering, and dielectric impedance measurements is used to systematically explore materials chemistries and building block functionalities for the creation of nano-porous heterogeneous electrolytes. By targeting enhanced stiffness, geometrically optimized Li+ migration paths, minimal dissipative coupling between cation and donor, and tunable redox potentials, these hybrid network structures are designed to exhibit unsurpassed performance as rechargeable battery electrolytes.