Eco-friendly materials for electrochemical capacitors

Electrochemical capacitors, also known as supercapacitors or ultracapacitors, due to their excellent electrochemical performances, attract significant interest as renewable energy storage devices, mainly when carbon-based materials are used as electrode components. Their low cost, availability, and sustainability are among the main benefits of activated carbons. This study reviews various biomass precursors, including coffee grounds, shells, husks, and other biomaterials. Processing methods of biomass precursors, e.g., pyrolysis, hydrothermal treatment, and chemical activation, affect the electrode porosity and surface area, as well as their electrochemical behaviour. According to the literature data, activated carbons obtained from coffee ground carbonisation achieve specific capacitances of 350 F g −1 , energy densities of around 34–39 Wh kg −1 , and show excellent cycling stability with the rate capability higher than 85% after 7000–9000 cycles. This study aims to highlight the potential of renewable waste-based carbons as promising electrode materials for next-generation energy storage systems.