UC San Diego

Enhancing the performance of secondary batteries is vital for the widespread adoption of renewable energy technologies such as electric transport, grid storage, and portable electronics. To increase the energy density of these systems, extensive efforts have focused on replacing the graphite anode in conventional Li-ion batteries with lithium metal, which boasts a high capacity of 3860 mAh g−1 and a low reduction potential of −3.04 V vs standard hydrogen electrode, making it an ideal choice. However, lithium metal batteries (LMBs) face a formidable challenge: limited cycle life caused by low reversibility and the pulverization of Li due to poor Li plating-stripping behavior. Despite advances in electrolyte design that have improved Li anode coulombic efficiencies to over 99.5%, further pushing up the value remains challenging. Hence, a comprehensive understanding of the mechanisms behind dense Li electrodeposition is crucial to maintain a low-porosity Li anode throughout the cycling process, extending the battery cycle life to facilitate the successful integration of renewable energy technologies.This dissertation outlines our efforts to comprehend and mitigate the pulverization process of the lithium metal anode during plating-stripping cycles, aiming to achieve long-cycle-life lithium metal batteries. In the first project, we develop a 3D carbon host for lithium deposition, where we discover that the pore size of the 3D host significantly influences the locations of lithium electrodeposition, vital for long-term stability. In the second project, we design a carbon-based substrate and observe that faceted Li seeds with a hexagonal shape can be uniformly grown on carbon-polymer composite films. Our investigation unveils the crucial role of carbon defects as nucleation sites for their formation. The presence of uniformly distributed crystalline seeds facilitates low-porosity Li deposition, effectively reducing Li pulverization during cycling, and enabling fast-charging capabilities for Li metal batteries. In the third project, we identify that non-uniform stripping of lithium leads to subsequent non-uniform, dendritic deposition, initiating a vicious cycle that results in lithium pulverization, cell shorting, or capacity degradation. To address this challenge, we engineer a lithium-carbon composite, which exhibits more uniform stripping and subsequent deposition on carbon particles. Our approaches address challenges during both stripping and plating processes, providing valuable insights for future designs of high areal capacity lithium metal anodes.