CAREER: Controlling two-dimensional heterointerface in layered oxides for electrodes with advanced electrochemical properties

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NON-TECHNICAL DESCRIPTION: This CAREER project aims to create a completely new class of ceramic oxide materials with advanced charge storage capabilities, opening a door to next-generation batteries with higher energy density, faster charging and a much longer lifetime. These new materials are two-dimensional (2D) oxide-based structures that are built by alternating oxide layers and electronically conductive layers, such as graphene-based compounds or transition metal carbides (MXenes). The resulting structures exhibit characteristics important for battery electrodes: space that allows ion movement, and conductive layers that enable fast transport of electrons. Combining layered metal oxides and carbon-based compounds in high quality layer-by-layer architecture offers an opportunity to discover and investigate new phenomena occurring at interfaces. This fundamental understanding is important for the creation of batteries with improved energy and power capabilities. The materials and methods developed in this work are relevant to a wider range of applications, including energy storage, electrochromics (responsible for reversible changes of colour), sensing, actuation (or control of movement), and water treatment. The interdisciplinary nature of this project attracts diverse undergraduate and graduate students to research. The project integrates synthesis and properties of 2D structures into the engineering curriculum at the PI's institution and enriches outreach programs through the creation of educational videos on synthesis and electrochemical properties of materials. A variation on the gameshow Family Feud focused on electrochemistry is being used to attract more students to STEM fields.TECHNICAL DETAILS: This research is focused on understanding how face-to-face heterostructured interfaces can be created and controlled in layered materials. The aim is to produce 2D oxide-based heterostructures with high electron and ion transport leading to improved energy storage capabilities in Li-ion, Na-ion and K-ion batteries. Layered transition metal oxides show high redox activity in intercalation reactions and relatively high working potentials, making them especially attractive for use as cathodes in energy storage devices. However, the low electronic conductivity of most oxides limits their performance. To overcome this limitation, layered oxides are combined in unique heterostructured architectures with electronically conductive 2D compounds by controllably alternating atomically thick layers of different individual materials. The 2D heterostructure electrodes are constructed using a sol-gel assisted transition metal oxide synthesis process through (1) chemical pre-intercalation of organic molecules followed by pyrolysis, or (2) addition of solid nanoflakes of conducting phases (graphene or MXene) during the sol-gel process. The improved understanding of the transport of ions and electrons and charge storage mechanisms in layered heterostructured materials achieved in this work is expected to lead to better electrodes and open exciting new research directions. The tailored 2D heterointerfaces make it possible to design new ceramic materials with tunable structures and compositions that exhibit high ion storage capability, rapid electron and ion transport, and enhanced electrochemical stability.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.