SusChEM: Collaborative Research: Holey Reduced-Graphene-Oxide Film for Na-Ion Battery Anode

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PI: Hu, Liangbing / Barone, VeronicaProposal Number: 1335979 / 1335944Institution: University of Maryland College Park / Central Michigan UniversityTitle: Collaborative Research: Holey Reduced-Graphene-Oxide Film for Na-Ion Battery AnodeDue to the low cost and earth abundance of sodium, Na-ion batteries (NIB) are emerging as a viable technology to meet the requirements for transportation and other energy storage applications. Rational structure designs that allow effective manipulation of electrons and ions in multiporous electrodes are critical. Although Na is much richer on earth than Li, Na ion has a much larger size, which poses grand challenges for Na-ion technologies. There has been an increasing interest on Na ion batteries in the past few years. Novel materials for cathodes, anodes, and electrolytes were recently reported. A few promising cathode materials are demonstrated, such as Na2/3Mn1/2Fe1/2O2, Na0.44MnO2 and NaMPO4 (M=Fe, Ca, Mn). For the anode electrode, hard carbon is shown to present a capacity of 250 mAh/g, but with a poor rate and cycling performance. High-performance and low cost anode materials are still needed for the success of Na-ion batteries. Two-dimensional carbon materials are promising as Na ions intercalate in the planes to achieve a highly reversible capacity; however, challenges exist in 2D carbon materials for Na-ion batteries. There is neither a successful demonstration of working electrodes, nor fundamental studies of Na ion storage mechanisms.In this project, experimental and computational tools will be combined to investigate and discern the three possible Na ion storage mechanisms: Na ion intercalation, cluster formation, and redox reactions with functional groups. Fundamental charge storage kinetics will also be studied. Rational nanostructures based on holey reduced graphene oxide (H-RGO) for high-performance Na-ion battery anodes will be designed by exploiting their fundamental charge storage mechanisms. Preliminary experiments on H-RGO detailed in this proposal, show promising results for the targeted applications. Results on controlled experiments agree well with preliminary computational predictions based on density functional theory. The proposed joint effort from experiments and computation will overcome the fundamental challenges in Na-ion battery anodes based on carbon nanomaterials.Much more challenging than Li-ion batteries, Na-ion devices require better materials design and electrochemistry science to achieve similar storage capacity (thermodynamics) and rate performance (kinetics). This project focuses on the materials structure and fundamentals related to the manipulation of Na ions in H-RGO nanostructures. Materials design, defects manipulation, nanoscale ion transport through holes, intercalation barriers, interactions with functional groups, Na cluster formation, etc., will be thoroughly investigated through a collaborative and synergistic approach between theory, computation, and experiments. From a pragmatic viewpoint, the proposed atomic level understanding will facilitate the optimization of anode materials to achieve Na specific capacities at high current density rates similar to the ones offered by Li-ion anodes, by exploiting the large surface area of H-RGO and controlling its chemical nature.The successful demonstration of carbon materials as anodes, coupled with the recent development of cathode materials, will enable the use of low-cost Na-ion technologies for energy storage. This will permit the incorporation of solar and wind energy into the renewable energy landscape. The research will be integrated in both graduate and undergraduate courses with the goal of attracting students to the area early in their careers. Research in a collaborative environment will also give undergraduate and graduate students opportunities to solve problems from both experiments and computations.