Low-cost AlCl3/Et3NHCl electrolyte for high-performance aluminum-ion battery

Abstract The aluminum-ion battery is a very promising rechargeable battery system for its high-power-density and three-electron-redox aluminum anode. Currently, the aluminum-ion battery is mainly composed of aluminum anode and graphitic cathode, separated by 1-ethyl-3-methylimidazolium chloride (EMIC)-based ionic liquid electrolyte. Despite of the progress made for cathode materials, its practical application is severely restricted by the high cost and low productivity of EMIC. Here we report a low-cost AlCl3/Et3NHCl room temperature ionic liquid electrolyte to fabricate practical yet high-performance Al-graphene battery. The battery shows 112 mAh g-1 cathodic capacity with 97.3% retention after 30,000 cycles and 84% retention even after an ultrahigh current density at 18 A g-1 (150 C, charged in 18 second). In this battery, electrochemical deposition/dissolution of aluminum at the anode while intercalation/de-intercalation of chloroaluminate anions in the graphene cathode take place during charge-discharge. The formation of a stage 3 graphene intercalation compound at fully charged state is confirmed. This pragmatic and cost-effective AlCl3/Et3NHCl room temperature ionic liquid grants the aluminum-ion battery with high performance and higher practical value.