Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Sun, Xueliang

Abstract

Li-metal batteries (LMBs) and Na-metal batteries (NMBs) are considered as the promising candidates to replace the conventional Li-ion batteries (LIBs) due to their high theoretical energy density. For LMBs and NMBs, Li metal and Na metal are the ultimate choices to achieve their high energy density due to the high specific capacity, low electrochemical potential and lightweight. However, as alkali metals, both Li and Na metal anodes suffer from serious challenges including 1) Li/Na dendrite formations and short circuits; 2) Low Coulombic efficiency (CE) and poor cycling performance; and 3) Infinite volume changes. This thesis mainly focuses on the design of multiple strategies for the stabilization of Li and Na metal anode for LMBs and NMBs.

The first part in the thesis demonstrates both atomic layer deposition (ALD) Al2O3 and molecular layer deposition (MLD) alucone as the protective layers for Li metal anode with effectively suppressed dendrite formation and improved cycle life in different electrolytes (carbonate-based and ether-based).

In the second part, a universal approach has been proposed to achieve a long lifetime and dendrite free Li metal anodes by introducing carbon paper (CP) as an interlayer.

To further improve the electrochemical performances, a bi-functional interlayer of CP with vertical nitrogen-doped carbon nanotubes (NCNTs) was designed for Li metal anode in the third part.

In the fourth part, ALD Al2O3 coating was fabricated for the protection of metallic Na anode in the ether-based electrolyte. By protecting Na foil with the ultrathin Al2O3 layer, the dendrites and mossy Na formation have been effectively suppressed and life has been significantly improved.

In order to solve the more serious issues in the carbonate-based electrolyte, the inorganic-organic coating alucone coating via MLD was deposited on Na anode, as discussed in the fifth part. The MLD alucone coating shows better performances than the ALD Al2O3 coating in the carbonate-based electrolyte.

In the sixth part, a solution-based method was developed to synthesize an artificial protective layer of solid-state electrolyte Na3PS4 (NaPS) on the surface of Na metal with more homogeneous Na plating/stripping process, resulting to the suppressed Na dendrite growth.

To further limit the volume change of Na metal anode, in the seventh part, the 3D Na composite electrode using CP-NCNTs as host was fabricated via the thermal infusion method with minimum volume change and dendrite-free Na deposition.

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