Investigation of Cost-Effective AlCl_3-Urea Ionic Liquid Analog for Al-Ion Batteries

摘要

The present study investigates the physicochemical properties of cost-effective AlCl_3-urea ionic liquid analogs (ILAs) for aluminum (Al)-ion batteries. The neutral and the acidic regions for AlCl_3/urea molar compositions were investigated using nuclear magnetic resonance spectroscopy (NMR), linear sweep voltam-metry (LSV), and electrochemical impedance spectroscopy (EIS) to determine the speciation of ionic moieties, electrochemical stability, and ionic conductivity of this complex system. The physical characterization shows that only 1.2-1.5 molar compositions are suitable for aluminum-ion batteries at room temperature, while 1.3 results in the highest ionic conductivity. The NMR results indicate that Al_2Cl_7~- is the dominating species for electrodeposition of aluminum at higher molar composition compared with AlCl_2-(urea)_2~+, while the relative amount of AlCl_4~- remains almost unchanged across investigated compositions. The aluminum-ion battery prepared using aluminum anode and graphene nanoplatelets cathode delivered a specific capacity of 60 mAh g~(-1) with 1.4 molar composition ILAs at 400 mA g~(-1).