Recovery of kitchen bio-waste from spent black tea as hierarchical biomorphic carbon electrodes for ultra-long lifespan potassium-ion storage

Abstract Spent black tea from kitchen bio-waste has been recycled to design an eco-friendly, green, and low-cost carbon electrode for high-efficient and super-long lifespan potassium ion storage. Profiting from the hierarchical porous structure, and co-doping effect, the novel KBT-7 electrode derived from kitchen bio-waste spent black tea carbonized at 700 °C harvests prominent electrochemical properties. When applied for potassium-ion batteries (PIBs), the anode delivers high reversible capacity of 491.6 mAh g−1 at 50 mA g−1, and remarkable long-term cycling durability of 102.1 mAh g−1 at 1 A g−1 even after 2300 cycles. In particular, when used for potassium-ion hybrid capacitors (PIHCs), the asymmetrical PIHCs display ultra-long term cycling property of 54.2 mAh g−1 even at 3 A g−1 after 10, 000 cycles, admirable rate ability of 51.7 mAh g−1 even at 6.4 A g−1, as well as superior high energy/power density. DFT analysis further demonstrates that the defects and N, P co-doping stimulate fast electron/ion-transport kinetics, thus enabling highly durable potassium storage property. This study presents a facile, scalable, and green strategy to prepare a high-performance biomorphic carbon electrode from kitchen bio-waste for promising potassium-ion storage applications.