Diffusion of Lithium in Boron-doped Diamond Thin Films

Sammanfattning: In this thesis, the diffusion of lithium was studied on boron-doped diamond (BDD) as a potential anode material in lithium ion batteries (LIB). The initial interaction between deposited lithium and BDD thin films was studied using X-ray Photoelectron Spectroscopy (XPS). Diffusion is directly linked to reactions between lithium and carbon atoms in the BDD-lithium interface. By measuring binding energies of core-electrons of carbon and lithium before and after deposition, these reactions can be analyzed. Scanning Electron Microscopy (SEM) was used to study the BDD surface and the behaviour of deposited lithium. Experiments show that a chemical interaction occurs between lithium and carbon atoms in the surfacelayers of the BDD. The diffusion of lithium is discussed from spectroscopic data and suggests that surface diffusion is occurring and no proof of bulk diffusion was found. The results do not exclude bulk diffusion in later states but it was not found in the initial interaction at the interface after depositing lithium. SEM images show that lithium clusters in the nanometer range are formed on the BDD surface. The results of this study give insights in the initial diffusion behaviour of lithium at the BDD interface and possible following events are discussed.