Supercharged Sustainability—Reimagining Lithium-Ion Batteries and Palm Loofah Fibers Waste as Cost-Effective Approach to High-Performance Solid-State Supercapacitors

Green solid-state supercapacitors made of recycled materials are of paramount importance. Recently, the rising demand for energy storage systems and the growing concern over electronic and biomass waste have prompted significant research efforts toward sustainable and efficient recycling methods. Researchers have achieved a good potential to recover many materials used in supercapacitor applications. From electronic waste, graphene and metal oxides can be extracted from spent batteries while carbon and cellulose materials can be extracted from biomass waste like wood chips and sewage sludge. The use of recycled materials in supercapacitors is a developing field with promising potential. However, most of the current research tests the recycled materials as 3-electrode supercapacitor systems, not as a real supercapacitor device that would be used in the commercial sector. Even when the research tests the recycled materials as a 2-electrode supercapacitor system, it would use liquid electrolyte which causes leakage and affects the stability of the device.<br/><br/>In this regard, this study aims to fabricate an asymmetric solid-state supercapacitor device using metals from battery waste (M-BW) and utilizing amorphous carbon recycled from agriculture waste (C-AW). Through simple and cost-effective recovery methods, the valuable metal oxides are extracted from spent lithium-ion batteries (LIBs) and purified hydro-metallurgically, ensuring their efficient reuse and reducing environmental impact. Furthermore, the potential of palm loofah is explored as a carbonaceous material for supercapacitor electrodes after its recovery using chemical and thermal activation.<br/><br/>The morphology and structure of both recycled materials (metal oxides and carbonaceous material) are characterized by different material characterization techniques like FESEM, HRTEM, XPS, etc. This carbon structure sandwiched with the recovered metal oxides and separated by KOH-PVA as a gel electrolyte, forms the basis for fabricating the solid-state supercapacitor device which exhibits excellent electrochemical performance. The device achieves a good specific capacitance (60 F g^-1) with high energy and power densities, and superior stability with up to 50,000 cycles of charges/discharges indicating its ability to efficiently store and deliver electrical energy. Moreover, the device retains its capacitance over multiple charge-discharge cycles with a retention rate of 100%. That proves the potential of using recycled materials in supercapacitor devices to promote sustainability, improve energy efficiency, reduce costs, and enhance performance. The fabricated M-BW//C-AW solid-state device achieves high performance and can compete with other counterpart devices fabricated from recycled materials and a wide range of newly synthesized ones.