Low-Cost AlCl3–GdnHCl Deep Eutectic Solvent Electrolyte for High-Performance Al/Graphite Batteries

Nonaqueous rechargeable Al batteries (RABs) have attracted significant research interest due to the extremely abundant reserves, high theoretical capacities, and low-cost. However, the commonly used nonaqueous RAB ionic liquid (IL) electrolytes are highly air-sensitive and high-cost, which seriously limits their commercial application. Herein, AlCl3–guanidine hydrochloride (AlCl3–GdnHCl), a new low-cost and environmentally friendly deep eutectic solvent (DES) with only 1/40 of the cost of [EMIm]­Al x Cl y is introduced into applications for nonaqueous RABs. The battery displays a discharge capacity of 128 mAh g–1 at 0.1 A g–1, which is significantly higher than that of 88 mAh g–1 in [EMIC]­Al x Cl y electrolyte. It can reach 124.6 mAh g–1 at 1 A g–1 with the Coulombic efficiency of 99.5% for 1000 cycles. According to the mechanism studies, during the charge–discharge cycle, the fast deposition/dissolution reaction of Al took place at the anode side, while intercalation/deintercalation reaction of [AlCl2(Gdn)n]+ ions and chloroaluminate anions [Al x Cl y ]− (i.e., Al2Cl7 – and AlCl4 –) occurred at the graphite cathode side. With such significant electrochemical behaviors, the AlCl3–GdnHCl DES possesses great potential for use in high-performance storage devices.