Maximizing the electrochemical performance of supercapacitor electrodes from plastic waste

The management of the increasing volume of plastic waste has become a key challenge for society. A promising strategy now consists in the transformation of plastic waste into high-value materials that can be utilized in energy storage devices such as batteries and supercapacitors. In this study, we demonstrate a two-step procedure, involving pyrolysis, followed by chemical activation that will convert common plastic waste into activated carbons (ACs). This technique makes ACs suitable for supercapacitor electrode materials. Further, the electrochemical performance of ACs is outstanding in terms of capacitance, energy density, and cycling stability. Besides the well-established parameters, including a specific surface area and micropore volume, we found that other critical factors such as polymer glass transition temperature, polymer-activating agent miscibility, activating agent (K₂CO₃):AC ratio, and AC water dispersion stability also play a crucial role in determining the supercapacitors performance. Controlling these parameters, we obtained ACs as supercapacitor electrodes from a range of plastic waste materials with a competitive electrochemical performance. Specifically, the ACs exhibited a specific capacitance of 220 F g⁻¹ (at a current density of 1 A g⁻¹), energy and power densities of 61.1 Wh kg⁻¹ and 36.9 kW kg⁻¹, respectively, and excellent cycling stability (95 % retention after 30,000 cycles). Our findings provide a pathway towards transforming plastic waste into valuable electrode materials for supercapacitors.