CAREER: Design and Understanding up from the Atomic Scale of Multivalent Intercalation Electrodes for High-Energy-Density Rechargeable Batteries

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There is a critical need for improved energy storage technologies for electric vehicles and large-scale integration of renewable electricity grid storage to improve domestic energy security. Currently, state-of-the-art energy storage technologies such as lithium-ion batteries have insufficient energy density and are too costly for broad use in these applications. Battery electrodes based on multivalent ions (e.g., aluminum ions or zinc ions) yield significant enhancements in electric charge storage capacity over monovalent (e.g., lithium-ion) electrodes. When paired with their corresponding metal electrodes, potentially transformative gains in energy density are possible. However, multivalent battery performance to date is lacking, in large part due to limited fundamental understanding and control of the complex electronic, chemical, and structural changes that the electrodes undergo upon continued charge and discharge cycles. Research efforts in this project will investigate the fundamental electrochemical processes that occur during the use of multivalent electrodes, yielding insights into how to design and realize rechargeable batteries with significantly enhanced energy storage properties. Rechargeable aluminum-ion and zinc-ion electrodes will be investigated as both aluminum and zinc metals are earth abundant, low-cost, non-flammable, non-toxic, and exhibit high volumetric charge storage capacity. The project also includes outreach efforts that will advance STEM education at the high school level by directly interacting with high school science teachers at a local high school via a "Battery Bootcamp". Outreach will stress the co-development of hands-on, age appropriate laboratory experiments for the high school students to use to help understand electrochemical engineering concepts. The project also will conduct a NMR School within the City University of New York (CUNY) for graduate students to incorporate this technique and other advanced spectroscopic methods to enrich their own respective research projects.The scientific and technological objectives of this research project are to (i) understand, up from the atomic scale, the processes and properties underpinning electrochemical intercalation of multivalent cations in crystalline transition metal compounds and (ii) to use this understanding to discover and optimize novel intercalation electrodes with significantly enhanced bulk energy storage properties. Aluminum-ion (Al3+) and zinc-ion (Zn2+) intercalation electrodes will be investigated to leverage the favorable electrochemical properties of aluminum and zinc metal while enabling the effects of differing ion valence and charge density to be studied. The electronic and crystalline structures of model transition metal compounds will be systematically varied, enabling investigations of their relationships to electrochemical intercalation phenomena from the molecular to the cell level. Subsequently, knowledge gained from model studies will be used to initiate targeted materials discovery efforts, wherein new electrode compositions and structures will be synthesized and explored for next-generation aluminum-ion and zinc-ion batteries. Novel multi-dimensional solid-state nuclear magnetic resonance (NMR) methods will yield new insights into the atomic-level environments, structures, and dynamics of intercalated cations and electrode frameworks, revealing ion intercalation and charge transfer mechanisms. Overall, this work is expected to establish and validate molecular design principles aimed at realizing multivalent intercalation electrodes with enhanced charge storage capacities, intercalation potentials, and rate properties.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.