Non-flammable electrolyte for Li-batteries for fuel cell vehicles and hybrid vehicles

In order to improve the safety of Li-batteries for HEVs and FCEVs, non-flammable liquid electrolyte using room temperature ionic liquids (RTILs) has been developed. RTIL is one of the promising candidates of the new electrolyte system because of the excellent thermal stability of RTILs. Among the various series of RTILs, 6-membered cyclic aliphatic and asymmetric quaternary ammonium-imide electrolyte works in Li/LiCoO2 cell as well as the organic electrolyte, and showed much better thermal stability when heated together with the electrode materials. Furthermore, the RTIL exhibited the self-extinguishing properties when mixed with the organic electrolyte with the 40 wt% or more. The trial cell showed almost no capacity degradation up to 1 CmA. The RTIL can be said to have a potential as a flame retardant additive for the organic electrolyte used in the Li-ion battery for HEVs and FCEVs.