Highly Graphitic N-Doped Biomass-Derived Hard Carbon with a Low Operating Potential for Potassium-Ion Batteries

Hard carbon is considered to be the most promising anode material for potassium-ion batteries (PIBs) because of its high storage capability and inexpensive cost, but most of them have a high operating potential. Herein, a highly graphitic nitrogen-doped hard carbon (NHC) is prepared by soaking a corn stalk in urea solution and calcination. NHC can deliver a reversible capacity of 402 mAh g(-1) in the first charge-discharge cycle and 87% of the total capacity is measured below 1 V versus K+/K. Simultaneously, it can retain a capacity of 263 mAh g(-1) after 100 cycles at 200 mA g(-1). Even at 1 A g(-1), it can still provide a capacity of 176 mAh g(-1) after 260 cycles. These superior electrochemical performances are attributed to the doping of graphitic nitrogen. Noticeably, such a biomass-derived NHC is not only environment friendly but also easy to prepare, which makes it a competitive anode material candidate for PIBs.