Microtubular Hard Carbon Derived From Willow Catkins as an Anode Material With Enhanced Performance for Sodium-Ion Batteries

As a kind of common bio-waste, willow catkin is of no economic value. But it is surprising that it can be an ideal carbonaceous source and bio-template for electrode materials of lithium-ion batteries and supercapacitors. Herein, we demonstrate that microtubular hard carbon can be derived from willow catkins and used as an anode of sodium-ion batteries (SIBs). The sample obtained from carbonization at 1000 °C delivers a high reversible capacity of 210 mAh g−1, good rate capability, and excellent cycling stability (112 mAh g−1 at 1000 mA g−1 after 1600 cycles) due to its unique tubular structure and the N-doping characteristic. The present work affords a new candidate for the production of hard carbon materials with tubular microstructure using natural biomass, and develops a highly promising anode material for SIBs.