Plastic-derived sandwich-like porous carbon nanosheet-supported hexagonal carbon micro-flakes for K-ion storage

Novel sandwich-like porous carbon nanosheet-supported hexagonal carbon micro-flakes (WPWMC) are fabricated via a one-step hydrothermal route at 700 °C with polyethylene as the precursor and magnesium as the inducer. Through various characterizations, it is confirmed that the hexagonal carbon micro-flakes exhibit (002) orientation, which exposes abundant edge active sites and shortens the K⁺ transmission path. Moreover, the inside cross-linked carbon nanosheets with abundant pores can accelerate ion diffusion and increase the capacitive contribution. The WPWMC anode displays a high reversible capacity (528.7 mA h g^-1 at 0.2 A g^-1), good rate capability (152.7 mA h g^-1 at 10 A g^-1) and long-term cycle stability (112.1 mA h g^-1 at 5 A g^-1 after 10 000 cycles). Furthermore, the WPWMC//CMK-3 hybrid capacitor exhibits an energy density of 222.7 W h kg^-1 at 446.2 W kg^-1. This work provides an idea for transforming waste plastic into value-added materials.