▎ 摘　　要

Reduced graphene oxide (rGO) has been prepared in an eco-friendly manner using precursors like graphite and external cover of waste metallic cases (aluminium (Al) and stainless steel (SS)) of spent lithium ion batteries (LIBs) in presence of hydrochloric acid (HCl). Four sets of rGO are prepared from graphene oxide (GO) at room temperature (RT), and at 70 degrees C; the as-synthesized samples are labelled as SSrGO-RT, SSrGO-70, AlrGO-RT, and AlrGO-70, respectively. The structure, morphology, BET surface area and porous nature of the synthesized materials are studied and checked their ability in supercapacitor application. Among the prepared rGOs, AlrGO-RT showed superior activity with a high specific capacity of 112 Fg(-1) at a current density of 0.5 Ag-1 due to its high surface area and mesoporous nature. Furthermore, it also displayed a high cycling stability of 20,000 cycles at a current density of 25 Ag-1. These results imply that such rGO synthesized from spent LIBs will be an inspiring asset material for the next generation high-performance supercapacitor. Moreover, rGO can be prepared in large scale by this waste to wealth approach and further be extended to synthesize other carbon based materials for various applications.