UNS: Dendrite-Free Storage of Lithium Metal in Porous Graphene Networks

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PI: Nikhil KoratkarProposal Number: 1510828Rechargeable lithium ion batteries support the development of sustainable energy systems by storing electricity generated by renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. A fundamental reliability issue with lithium ion batteries is the formation of lithium metal whiskers within the battery that ultimately short out the battery, creating a potential fire hazard and reducing battery life. The goal of this project is develop a lithium ion battery electrode which contains a form of carbon called porous graphene that will be designed to suppress this detrimental process. The project will seek fundamental understanding of lithium metal formation on the porous graphene and then use this information to design a higher performance, and safer, lithium ion battery. The educational activities associated with this project include the development of interactive learning module on lithium ion batteries for engineering classroom use, and outreach on nanotechnology topics to local high schools.A fundamental problem with lithium ion batteries for electrochemical energy storage is the eventual formation of lithium metal dendrites resulting from the plating of lithium metal on the outside surface of the anode, as opposed to within the anode where it is needed for high-energy density storage. These microscopic projections grow upon repeated cycling and ultimately pierce the separator, touch the cathode, and short out the device. The overall goals of the proposed research are to develop a fundamental understanding of lithium metal plating and dendrite formation in microporous graphene anodes, and then to use this information to develop micro-structured porous graphene networks that suppress dendrite formation and confine lithium metal plating within the porous network. Towards this end, the research plan has four objectives. The first objective is to understand the role of graphene defects in attracting lithium ions and initiating the plating mechanism. The second objective is to tune the type and density of defects in graphene in order control lithium metal storage within porous graphene networks. The third objective is to explore how mechanical confinement and electric field modulation effects can be used to suppress the formation of lithium dendrites in porous graphene structures. Finally, under objective 4, the kinetics of lithium ion diffusion though porous graphene structures will be characterized. A combination of detailed Ab initio and molecular dynamics simulations, as well as X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (IES), SEM, and TEM, will be the tools used carry out these objectives. Fundamental understanding obtained under these four objectives will be used to fabricate a lithium ion battery with microstructured porous graphene anodes designed to suppress lithium metal dendrite formation. Performance will be assessed through energy density, power density and charge/discharge cycling measurements. The research results will be used to develop an interactive virtual laboratory on the design of graphene based electrode structures for Li-ion rechargeable batteries for use in an undergraduate mechanical systems laboratory course.