Document Type

Dissertation - Open Access

Award Date

2020

Degree Name

Doctor of Philosophy (PhD)

Department / School

Electrical Engineering and Computer Science

First Advisor

Qiquan Qiao

Keywords

3D Current collector, Artificial SEI, Energy storage, Lithium dendrite, Lithium metal battery

Abstract

Lithium (Li) metal has been considered as one of the most promising anode materials to replace conventional graphite for Li-ion battery due to its high theoretical capacity (3860 mAh g-1) and low electrochemical potential (-3.04 V vs standard hydrogen electrode). However, it still faces some problems such as unstable solid electrolyte interphase (SEI), uncontrolled Li dendrites growth, and infinite volume change during battery charging/discharging. To develop a stable and low-cost Li metal anode for next-generation Li metal battery, in this dissertation, we have made efforts to understand and solve these problems in two aspects, by introducing an artificial SEI and constructing a 3D porous current collector. Firstly, a multifunctional artificial SEI protective layer was designed via using a nitrogen plasma treatment on the Li metal. A highly [001] oriented Li nitride (Li3N) layer was formed on the surface of Li metal with a plasma activation time of fewer than 5 minutes. Due to its high Young’s modulus (48 GPa) and high ionic conductivity (5.02×10- 1 mS cm-1), the Li3N artificial SEI layer blocked the direct contact between reactive Li metal and the liquid organic electrolyte, and suppressed the Li dendrite formation. Secondly, a highly flexible copper (Cu)-clad carbon framework (CuCF) current collector was designed for Li metal batteries. The pyrolysis of melamine-formaldehyde foam and following Cu electrodeposition were employed to fabricate the CuCF. The advanced current collector exhibited excellent flexibility with uniformly distributed Li nucleation sites on its surface. The cross-linked fiber network structure with large space could accommodate the volume change, while the high surface area and uniformly distributed Li nucleation sites led to the quench of the formation of Li dendrites. As a result, a dendrite-free Li metal anode was achieved in both circumstances. The Li3N artificial SEI and CuCF both gave rise to a stable Li plating/stripping with high Coulombic efficiency. In both cases, Li/LCO or Li/LFP full cells exhibited a long cycling life at a high current density of 1C. Furthermore, the Li deposition behavior with an artificial SEI and 3D current collector was also studied and compared with bare Li in the dissertation. The methods and strategies we used in the dissertation can provide a facile approach to realize a stable and safe Li metal anode for next-generation Li metal batteries.

Library of Congress Subject Headings

Lithium ion batteries.
Energy storage.

Format

application/pdf

Number of Pages

135

Publisher

South Dakota State University

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Rights Statement

In Copyright