Reuse of waste lithium by-product graphite in low-cost rechargeable aluminum batteries

Abstract

Rechargeable aluminum batteries (RABs) are considered promising candidates for large-scale energy storage devices due to their remarkable characteristics in terms of theoretical energy density, safety, environmental friendliness, and sustainability. However, the proper selection of cathode materials and the high price of suitable electrolytes have greatly delayed the process of their commercial application. In this study, a cost-effective RAB module consisting of regenerated graphite (RG) from lithium-ion batteries recovery process as cathode and NaCl-KCl-AlCl₃ low-temperature molten salt as electrolyte is reported. At an operating temperature of 110 °C, the Al/RG battery demonstrates a promising electrochemical performance. After 1000 cycles at a current density of 0.5 A g⁻¹, RG retains a discharge-specific capacity of 114.7 mAh g⁻¹ (the highest is 133.6 mAh g⁻¹), superior to 99.1 mAh g⁻¹ for natural graphite as a contrast under equivalent conditions. The underlying mechanism governing the Al/RG battery is further elucidated that RG preserves its crystalline structure while successfully eliminating most of impurities and exhibits an enhanced interlayer spacing during the post-recycling. Furthermore, information on the price of by-product graphite produced during commercial recycling was collected, which shows that its cost could be as low as 0.07 USD kg⁻¹. This research not only advances the recycling of by-product graphite during recovery processes but also highlights remarkable electrochemical performance in economically viable molten salt RABs, thereby offering novel insights for large-scale commercial energy storage applications utilizing RAB technology.