Transformation of Spent Li‐Ion Battery in to High Energy Supercapacitors in Asymmetric Configuration

For the first time, herein we report a new track to regenerate the Mn−Co carbonate (MCC) from the mixed composition of cathodes of spent LIBs and successfully evaluated as an electrode material for supercapacitor applications (ASC). The resultant MCC spheres are first tested in a half cell with Pt‐strip as the counter electrode using neutral and alkaline electrolytes. The fabricated ASC with regenerated MCC as the positive electrode and commercial activated carbon (AC) as the negative electrode in the presence of 6 M KOH reveals a specific capacitance of 119 F g−1 at 0.5 A g−1, also could retain 65 F g−1 at a high current density of 4 A g−1 accompanied by outstanding cycling stability of 9000 cycles with 60 % retention at 1.5 A g−1. Furthermore, this low‐cost ASC MCC//AC offers a high energy density of 42.2 Wh kg−1 at a power density of 1.6 kW kg−1, in a stable potential window of 0–1.6 V. In addition, the flexible ASC in solid‐state assembly in series efficiently power a green light‐emitting‐diode, inspiring its promising practical application to build new ASC using spent LIBs materials as sources in “waste‐to‐wealth” approach for high energy asymmetric all‐solid‐state supercapacitors. Waste‐to‐Wealth: Mn−Co carbonate was resynthesized from the different manufacturers of spent lithium‐ion batteries, and evaluated as a cathode in the asymmetric supercapacitor offering low‐cost energy storage device for sustainable use.