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.