UC San Diego

Li-ion batteries have become an attractive key component in energy storage systems as the worldwide energy infrastructure shifts towards being more environmentally concerned. The development of Li-ion batteries has also been pressured from the rapid growth of modern technologies such as mobile electronic device and an electric vehicle based transportation society. However, unlike the fast pace development of other aspects of these technologies, the development of better Li-ion batteries has remained a limiting factor. Therefore, today’s technology market demands the appearance of new Li-ion battery system with higher energy density. To satisfy this demand, Li-ion batteries must advance beyond intercalation cathode materials. Transition metal chloride cathode conversion materials show promise of a new paradigm in energy storage system due to their relatively high energy density. However, disintegration of metal chlorides remains a critical issue in application to a battery.

In this thesis, highly concentrated electrolytes that consist of 0.1M LiCl/6M LiTFSI and 0.1M LiCl/0.1M LiNO3/6M LiTFSI in TEGDME solvent is introduced to effectively suppress the dissolution of cathode materials. Among metal chloride materials, CoCl2 and NiCl2 show promise with high capacities of 160 mAh g-1 and 330 mAh g-1, up to 40% and 80% of their theoretical capacities respectively, in a superconcentrated electrolyte with LiNO3 additive introduced to protect the lithium surface. NiCl2 in a properly treated electrolyte (0.1M LiCl/0.1M LiNO3/6M LiTFSI in TEGDME) showed the most promising behavior with stable cycling and low hysteresis ~ 0.5 V as a new positive electrode material to replace intercalation based rechargeable battery.