Sustainable activated carbon for aqueous and flexible zinc-ion energy storage
Rudransh Dev, Himanshu Gupta, Himanshu Gahtori, Hem Kanwar Rathore, Muruganandham Hariram, Manoj Kumar, Prashanth W. Menezes, Debasish Sarkar
Abstract
Carbons with high specific surface area (SSA), hierarchical porous structure, and abundant surface functionalities are highly desirable for electrodes in high-performance electrochemical energy storage systems. Here, we have explored bitter apple peel, a biomass waste, to derive carbons with such desirable traits and investigated its electrochemical performance as active material in aqueous supercapacitor (SC) and zinc-ion hybrid SC (ZIHSC). Benefited by its high SSA (1475.3 m 2 /g) and surface oxygen functionalities (C-O, C=O, etc), the optimised activated carbon (BAC-3) demonstrated excellent electrochemical performance. When tested as an aqueous SC cathode, the BAC-3 demonstrates a specific capacitance of 178.5 F/g at a high current density of 5 A/g, and no capacity degradation after 10,000 CV cycles. To improve its energy performance further, the zinc-ion storage traits of the synthesised materials are also investigated. As an aqueous ZIHSC cathode, the optimised BAC-3 achieved exceptional energy and power densities of 147.6 Wh/kg and 4.5 kW/kg, respectively, and showed ultra-stable capacitance over 100,000 cycles. Even the hydrogel-electrolyte based ZIHSC assembled with BAC-3 cathode and Zn anode reached an energy density as high as 135 Wh/kg, exhibited good flexibility and cycling stability, and successfully powered a red LED, suggesting promising practical application prospects. The work provides critical insights into biomass-resource utilization for value-added products for a sustainable environment and economy.