Document Type

Dissertation - Open Access

Award Date

2024

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agricultural and Biosystems Engineering

First Advisor

Zhengrong Gu

Abstract

Graphene, a prevalent anode material in commercial lithium-ion batteries, has reached its theoretical capacity limit. The imperative is to develop high-capacity anode materials to meet the growing demand for energy density. Lithium metal, renowned for its exceptionally high theoretical specific capacity density (3680 mAh g-1) and low reduction potential (-3.04 V, relative to the standard hydrogen electrode), is commonly dubbed the "Holy Grail" for negative electrode materials in high-energy-density batteries. However, practical advancements in lithium metal anodes face obstacles like low Coulombic efficiency, limited cycle life, and heightened reactivity to the electrolyte and internal short circuits resulting from lithium dendrite growth. In electrochemical systems, the current collector acts as the substrate for lithium metal deposition/stripping, and its surface properties significantly influence the cycle stability of the lithium metal anode. This dissertation systematically designs various interface modification strategies to stabilize lithium metal anodes, considering the surface composition and microstructure design of the anode current collector. The dissertation introduces three innovative surface engineering strategies for modifying copper foil current collectors. Firstly, a three-dimensional structural copper pyramid array (CPA@CF) is formed on a flat copper foil (CF) through a straightforward electrodeposition method. This distinctive CPA@CF, featuring a substantial surface area and a porous 3D structure, enhances the diffusion of lithium ions and facilitates charge transfer, effectively mitigating the volume change of Li. In the second approach, three-dimensional lithiophilic gold (Au)-coated copper (Cu) pentagonal pyramid arrays (Au@CuPPA) are engineered on copper foil utilizing a combination of electrodeposition and chemical reduction methods. With lithiophilic layers and a 3D porous structure, the Au@CuPPA enhances the deposition/stripping process of lithium ions and reduces nucleation overpotential. Finally, a facile method is presented where 3D structured cuprous oxide (Cu2O) dendrites are grown on flat copper foil through a simple process involving electrodeposition and subsequent high-temperature treatment. The lithophilic Cu2O layer formed further establishes a favorable channel for the rapid diffusion of lithium ions (Li+) at the solid-liquid interface. The staggered stacking of Cu2O dendrites forms a 3D structure with a significantly increased specific surface area, alleviating current density and promoting the uniform distribution of Li flow. The objective of this dissertation is to establish a lithiophilic interface and devise micro-nano structures on the copper current collector, effectively governing the stable deposition of lithium metal, thereby seeking to advance the practical implementation of lithium metal anodes in high-energy-density battery systems.

Publisher

South Dakota State University

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Rights Statement

In Copyright