Freestanding CNT-modified graphitic carbon foam as a flexible anode for potassium ion batteries

Potassium-ion batteries (KIBs) have attracted more and more attention because of the abundant resources and low cost of potassium. The development of KIBs has been hindered due to the lack of electrode materials with high reversible capacity and long cycle life. Graphitic carbon as an anode for KIBs shows poor cyclability because the insertion of K-ions leads to huge volume expansion and structural collapse. Herein, we design carbon nanotube (CNT) modified graphitic carbon foam (CNTs/GCF) with 3D porous interconnected nanoarchitecture to boost the cyclability and rate performance of KIBs. The CNTs/GCF exhibits excellent electrochemical performance in terms of reversible capacity (226 mA h g−1 after 800 cycles with a capacity retention of 98% at 0.1 A g−1), cycle life (127 mA h g−1 after 2000 cycles with a capacity retention of 96% at 0.5 A g−1) and rate capability (254, 233, 204, 113, 85 and 74 mA h g−1 at 0.05, 0.1, 0.2, 0.5, 0.8 and 1 A g−1). The highly conductive CNTs shorten ion diffusion paths and the 3D GCF network facilitates electron transport and promotes the rapid migration of electrolyte ions. In situ Raman spectra prove that the CNTs/GCF shows the hybrid potassium storage mechanism of surface adsorption and intercalation.