In response to the need for sustainable energy storage solutions aligned with the European Green Deal, this thesis explores the development of next-generation supercapacitors using scalable and eco-friendly methods. The research integrates waste-derived activated carbon, water-processable binders, and sustainable electrolytes to create an environmentally responsible supercapacitor production process. Chapter 1 introduces the global energy landscape, emphasizing the role of supercapacitors in reducing fossil fuel dependence. The study is structured into three key areas. Chapter 2 focuses on the valorization of biodigester waste into high-performance activated carbon, achieving a surface area of 1867 m²/g and capacitance of 200 F/g in aqueous KOH. Prototypes demonstrated double the capacitance of commercial devices, validating industrial scalability. Chapter 3 investigates biodegradable binders and water-soluble separators as sustainable alternatives to conventional toxic materials. Pullulan-glycerol binders supported large-scale electrode production, achieving a high active material content and competitive performance with green electrolytes like γ-valerolactone and propylene carbonate. Pouch cells assembled with these materials exhibited an energy density of 17 Wh/kg and a power density of 7 kW/kg, with low degradation over cycling. Chapter 4 introduces alternative electrolytes, including water-in-salt electrolytes (WiSE) and deep eutectic solvents (DES), to enhance the electrochemical stability window and increase cell voltage. Symmetric EDLCs with WiSE using potassium acetate achieved superior stability (1.7 V vs. 1.2 V) and capacitance retention over 6000 cycles. Additionally, a patent-pending hybrid redox capacitor using DES-based electrolytes with redox-active species reached an energy density of 108 Wh/kg and a specific power of 30 kW/kg. This research demonstrates the feasibility of sustainable supercapacitors by integrating waste-derived materials, biodegradable binders, and novel electrolytes. The findings contribute to advancing green energy storage technologies, supporting renewable energy systems and electric mobility, while addressing industrial scalability and market applicability.
Elisabetta Petri (Wed,) studied this question.