Alon Shapira, MSc candidate
Department of Material Science and Engineering
Li-ion battery (LIB) is the champion in the rechargeable battery field. LIBs serve us in our everyday life powering our laptops, power tools, cell phones and cars.
The search for better cathode materials replacing LiCoO2 is an ongoing research in recent years. High voltage cathode materials supplying high power density or high energy density such as the spinel LiMn1.5Ni0.5O4 (LMNO) and the layered material LiNixMnyCo1-x-yO2 (NMC) are promising candidates to fuel the next generation of electric cars. However, LIBs based on those materials suffer from low cycability, particularly at elevated temperatures (45°C). Among the reasons for the capacity fading is leaching of Manganese (Mn) ions from the cathode. Once leached out, the Mn ions are migrating through the separator to the anode and eventually precipitating on the anode, thus blocking Li ions from intercalating into the anode.
In this research a several nanometers thick metal fluorides (MgF2, AlF3) coating layer was coated on the cathode material using Atomic Layer Deposition (ALD) process in a Fluidized Bed Reactor (FBR). The coating was done on the cathode material in its powder form before processing it into a cathode for a battery. The metal fluorides coating layer actually reduces the Mn dissolution from the cathode matrix via the formation of a stable and durable coating layer being also highly permeable for Li ions. Electron microscopy analysis (SEM and TEM) was performed for the pristine and coated powder. In addition, electrochemical analysis in a half-cell and full cell configuration was performed showing a substantial improvement in the capacity retention even at 45°C.
Supervisor: Prof. Yair Ein-Eli