Quenching Thermal-Runaway in Lithium Ion Battery By Hyperbranch Cathode Additives

One major issue in lithium ion battery is the safety where numerous explosion events created public concern and prevented it from wider application to transportation sector. The safety issue is primarily originated from the use of volatile organic solvent such as,EC, PC, and DMC.etc that contains thermally decomposible lithium salts (LiPF6, LiClO4 etc.).  Few approaches are explored to improve the lithium battery safety:, (a). The use of electrode materials without oxygen release (LiFePO4). (b). use of non- volatile solid-state electrolytes (ionic liquids). (c). use of non-flamable or fire retardant separator material (ceramic) (d). External electronic circuit protection, and (e)Shut down the thermal run-away by the use of additives. This paper disclosed results of a hyperbranch additive which can be thermally triggered to quench the oxyge release, block the combustion chain reaction, and accomplished successfully an active protective shut down. Furthermore, the additive forms porous protective layer (less than few nm) which hinders thick SEI formation and prevent direct electrolyte contact with the active material thus improves cycle-life.  Finally, the hyperbranched layer with flexible side chain created fast lithium ion transport path across/from the active materials, and improves high rate performance.  Details of the structure of the hyperbranched additives will be discussed.