Doctoral Dissertations

Alternative Title

First principles studies of complex hydrides for lithium ion battery and hydrogen storage applications

Abstract

"We employ density functional theory in a computational study of two energy storage systems.

In the first, we explore the thermodynamic viability of light metal hydrides as a high capacity Li-ion battery negative electrode. Given a set of solid-state and gas-phase reactants, we have determined the phase diagram in the Li-Mg-B-N-H system in the grand canonical ensemble as a function of lithium electrochemical potential. We present computational results for several new conversion reactions with predicted capacities between 2400 and 4000 mAhg⁻¹ that are thermodynamically favorable and that do not involve gas evolution. We provide experimental evidence for the reaction pathway on delithiation for the compound Li₄BN₃H₁₀ and compare with our theoretical prediction. The maximum volume increase for these materials on lithium insertion is significantly smaller than that for Si, whose 400% expansion hinders its cyclability.

In the second study, we attempt to gain understanding of recent experimental results of lithium borohydride nanoconfined in highly ordered nanoporous carbon. The carbon environment is modeled as a single sheet of graphene, and adsorption energies are calculated for nanoparticles of the constituent phases of LiBH₄ desorption processes (LiBH₄, LiH, lithium and boron). We find good agreement with previous studies of a single lithium atom adsorbed onto graphene. We predict that infiltrated LiBH₄ will decompose such that boron is trapped in carbon vacancies, and that the resulting boron doping is required to achieve negative wetting energies for the remaining LiBH₄. Desorption enthalpies are found to increase with shrinking cluster sizes, suggesting that the observed lowering of desorption temperatures is a kinetic effect although interactions with the carbon surface itself are predicted to have an overall effect of decreasing the desorption enthalpy"--Abstract, page iii.

Advisor(s)

Majzoub, Eric H.
Medvedeva, Julia E.

Committee Member(s)

Stein, Keith
Yamilov, Alexey
Fraundorf, Phil

Department(s)

Physics

Degree Name

Ph. D. in Physics

Sponsor(s)

Boeing Company
Missouri Space Grant Consortium

Comments

Dissertation completed as part of a cooperative degree program with Missouri University of Science and Technology and the University of Missouri--St. Louis.

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2011

Journal article titles appearing in thesis/dissertation

  • DFT predictions of high-capacity metal hydride conversion materials for Li-ion batteries
  • DFT study of nanocluster lithium borohydride energetics on carbon nanoscaffolds

Pagination

xi, 146 pages

Note about bibliography

Includes bibliographical references (pages 138-145).

Rights

© 2011 Timothy Hudson Mason, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Energy storage -- MaterialsFourier transformations -- Mathematical modelsHydridesLithium cells

Thesis Number

T 9900

Print OCLC #

795183325

Electronic OCLC #

908853666

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