Directional modification of oxygen functional groups by N heteroatoms on soft/hard carbons for sodium storage.

Different oxygen functionalization processes occur for N-doped soft carbon (N-SC) and hard carbon (N-HC), and there may be a competitive relationship between the formation of pyridinic-N and CO groups. For N-SC, abundant CO groups and defects bring excellent Na + storage performance and cycling stability, especially at high current densities.