DEVELOPMENT OF CARBONATE ELECTROLYTES FOR LITHIUM METAL ELECTRODES

The development of energy storage technology is an important topic for facilitating the employment of renewable energy in society. Therefore, current energy storage research is heavily focused on enabling rechargeable high-energy density lithium-based batteries. In particular, permitting reversible electrochemical plating and stripping of the lithium metal negative electrode (or lithium metal anode) in carbonate electrolytes can achieve this goal. Unfortunately, the performance of the lithium metal anode in carbonate electrolytes is plagued by unsafe dendrite formation and poor Coulombic efficiency upon cycling. This dissertation attempts to reveal the role of the composition and structure of the Solid Electrolyte Interphase (SEI) in relation to the performance of the lithium metal anode. Galvanostatic voltammetry was used to characterize the electrochemistry of the lithium metal anode, with Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, and Transmission Electron Microscopy to investigate the surface of the lithium metal anode. In chapter 2, a method to electrochemically synthesize lithium metal such that a reliable SEI is generated is introduced, using Cu||LiFePO4 cells. Using this method, in conjunction with the analytical techniques described above, chapters 3 and 4 investigates electrolyte components that significantly improve the performance of the lithium metal anode, fluoroethylene carbonate (FEC) and lithium difluoro(oxalate) borate (LiDFOB), with an explanation proposed. Finally, chapter 5 shows how FEC and LiDFOB can work together to optimize the SEI composition and structure, hence optimizing the performance of the lithium metal anode in carbonate electrolytes