A Flexible Multi-Channel Hollow CNT/Carbon Nanofiber Composites with S/N Co-Doping for Sodium/Potassium Ion Energy Storage

Carbon fibrous materials are the promising candidate for the anode of flexible sodium-ion batteries and potassium-ion batteries due to the structural advantages. However, the progress of mechanically robust anode materials with high electrochemical properties is still unsatisfactory for the flexible electrodes. Herein, the comprehensive design of the morphology with unique multi-channel hollow 1D/1D carbon nanotube/carbon nanofiber network and the lattice structure of carbon with S/N co-doping has been proposed. Benefiting from the enlarged interlayer spacing and the flexible fibrous network, the S/N doped carbon nanotube/carbon nanofiber composites (CNT/SNCF) possess not only high conductivity but also good structural stability during sodiation and potassiation processes. When used as anode materials in SIBs and PIBs, the free-standing CNT/SNCF electrodes exhibit high discharge capacities (274.1 and 212.5 mA h g–1 at 1 A/g after 1000 cycles, respectively), superior cycle stability (150.4 and 100.1 mA h g–1 at 5 A/g after 5000 cycles, respectively) and rate performance (109.3 mA h g–1 at 10 A/g and 108.7 mA h g–1 at 5 A/g, respectively), showing great prospects in flexible energy storage devices.