Commercial expanded graphite as high-performance cathode for low-cost aluminum-ion battery

Abstract Aluminum-ion battery (AIB) is a very promising rechargeable battery system for its safety and three-electron-redox aluminum anode. However, the low cost-effectiveness and performance limit its practical application, thus requiring low-cost cathode-electrolyte system with large-scale manufacturing potential. In this work, we successfully achieved a low-cost and high-performance AIB system consisting of commercial expanded graphite (EG) cathode and AlCl 3 -triethylamine hydrochloride (AlCl 3 -ET) electrolyte. The assembled AIB exhibited the cathode capacity of 78.3 ± 4.1 mAh g −1 (156.6 ± 8.2 mAh cm −3 ) at 5 A g −1 with 77.5% retention after 30 000 cycles. Even at a high active material loading of 6.16 mg cm −2 , the EG cathode displayed 101 mAh g −1 (207 mAh cm −3 ) at 1 A g −1 with 95.5% retention after 11 500 stable cycles. We confirmed the part of the cathode capacity was contributed by AlCl 4 − deposition, and the reaction mechanism of our new system resulted from the special structure of EG, which served as an important supplement of the classical mechanism of AIB. The high capacity of EG-AIB was contributed by AlCl 4 − deposition and its stage 4 intercalation. This work provides a very promising and simple strategy for establishing the low-cost, high-performance and high-mass loading AIB system with great commercial value.