Activation-free N-doped porous carbon to enhance surface-driven K storage vs intercalation dominated Na storage

Abstract

Carbonaceous materials show more and more obvious applications in potassium (K) ion battery (KIB) and sodium (Na) ion battery (NaIB) because K and Na have higher reserves than lithium (Li). However, the rate performance and cycle stability of KIBs and NaIBs are still hindered by huge volume change during ions insertion-extraction process and poor kinetics caused by larger volume of K+ and Na+ ions. Compared to graphite and hard carbon, nitrogen (N)-doped porous carbonaceous materials may provide good interfacial wettability and numerous ion transport channels, but low first coulombic efficiency is detrimental to the application of full-battery. Here, N-doped porous carbon (NPC) with a providential specific surface area is synthesized by a facile and activation-free way. Benefiting from N-doping and porous structure, KIBs and NaIBs display an enhanced rate capacity and cycle performance. The storage mechanism and kinetic characteristics of K and Na ion during charge and discharge are also discussed. Comprehensive performance indicates that NPC can obtain a better improvement in surface-driven KIBs than intercalation dominated NaIBs, and can provide some new design concepts for practical applications.