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Title:Directed lithium transport in high capacity lithium-ion battery electrodes
Author(s):Goldman, Jason
Director of Research:Nuzzo, Ralph G.
Doctoral Committee Chair(s):Nuzzo, Ralph G.
Doctoral Committee Member(s):Gewirth, Andrew A.; Braun, Paul V.; Rogers, John A.; Dillon, Shen J.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Energy Storage
Abstract:Lithium-ion batteries enable a modern, mobile society and are a widely used source of portable energy storage. Chapter 1 provides background and motivation for improving lithium-ion battery performance. Specifically these batteries still need improvements in terms of specific energy, specific power, cycle life, and safety. The rest of this document describes experiments utilizing model semiconductor electrodes to investigate fundamental phenomenon occurring during the operation of lithium-ion batteries in order to improve battery performance. Chapter 2 examines the crystallographic anisotropy of strain evolution in model, single-crystalline silicon anode microstructures on electrochemical intercalation of lithium atoms. We highlight model strain-limiting silicon anode architectures that mitigate these impacts. By selecting a specific design for the silicon anode microstructure, and exploiting the crystallographic anisotropy of strain evolution upon lithium intercalation to control the direction of volumetric expansion, the volume available for expansion and thus the charging capacity of these structures can be broadly varied. Chapter 3 examines the properties of microstructured Ge electrodes for Li-ion battery applications. Unlike Si electrodes, Ge electrodes do not exhibit the same anisotropic electrochemical lithium insertion. Model microfabricated single-crystalline Ge electrode structures are used to investigate the effect of microstructure design, coatings, and partial discharging on cycle life. These results provide an understanding of the effects of electrochemical processes on model microstructured Ge electrodes which may ultimately aid in the development of high capacity anodes for Li-ion batteries. In-situ characterization of lithium-ion batteries utilizing x-ray microscopy, nuclear magnetic resonance, transmission electron microscopy, and scanning probe microscopy have recently been utilized to understand fundamental phenomena occurring during (dis)charge cycling. X-ray Reflection Interface Microscopy (XRIM) was recently demonstrated by Fenter et al. utilizing the Advanced Photon Source at Argonne National Lab. In Chapter 4 we used full-field x-ray reflection interfacial microscopy in order to image the extent of the lithiation and the degree of residual crystallinity in individual silicon micro-posts directly. Images of the silicon posts are interpreted using a novel, but straightforward, model relevant for XRIM images obtained from large scale topological features. This approach should be widely applicable to a broad range of battery materials and for probing the liquid/solid interfaces of complex heterostructures during lithiation reactions. In chapter 5 we examine encapsulated micropore-modified silicon anodes that define lithium mass-transfer dynamics to constrain strain evolution and improve capacity retention during (dis)charge cycling. Fully integrated cells incorporating this silicon anode and a commercial grade LiCoO2 cathode maintain their capacity for 110 cycles with >99% average coulombic efficiency from cycles 5 to 100. Anodes with thicknesses up to 50 µm resulted in area-normalized capacities of up to 12.7 mAhcm-2. When the silicon anode microstructure pitch is varied, a direct relationship is found to exist between the rate capability and volumetric capacity of the anode. Helium-ion Microscopy, Secondary Ion Mass Spectrometry, and Scanning Electron Microscopy, used as ex-situ characterization methods for the evolution of the electrode’s structure on cycling, reveal significant changes in nanoscale morphology that otherwise retain the essential laminate micropore motif of the initial Si anode. The first appendix chapter uses recent advancements in terms of electrode coating and fabrication in order to demonstrate a solid-state battery using an inorganic solid-state electrolyte. We investigate whether cathode materials printed into channels could be utilized as a demonstration of a printed battery. Also the ability of conformal, thin ALD coatings of Al2O3 or LiAlOx to act as both separator and electrolyte was also tested. Neither ALD coating had the performance metrics required to serve as both separator and electrolyte. The second appendix chapter details our investigation of the impact of tetraethoxysilane (TEOS) as an electrolyte additive.
Issue Date:2014-05-30
Rights Information:Copyright 2014 Jason Goldman
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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