Boosting the K+-adsorption capacity in edge-nitrogen doped hierarchically porous carbon spheres for ultrastable potassium ion battery anodes

Abstract

Although carbon materials have great potential for potassium ion battery (KIB) anodes due to their structural stability and abundant carbon-containing resources, the limited K⁺-intercalated capacity impedes their extensive applications in energy storage devices. Current research studies focus on improving the surface-induced capacitive behavior to boost the potassium storage capacity of carbon materials. Herein, we designed edge-nitrogen (pyridinic-N and pyrrolic-N) doped carbon spheres with a hierarchically porous structure to achieve high potassium storage properties. The electrochemical tests confirmed that the edge-nitrogen induced active sites were conducive for the adsorption of K⁺, and the hierarchical porous structure promoted the generation of stable solid electrolyte interphase (SEI) films, both of which endow the resulting materials with a high reversible capacity of 381.7 mA h g^-1 at 0.1 A g^-1 over 200 cycles and an excellent rate capability of 178.2 mA h g^-1 at 5 A g^-1. Even at 5 A g^-1, the long-term cycling stability of 5000 cycles was achieved with a reversible capacity of 190.1 mA h g^-1. This work contributes to deeply understand the role of the synergistic effect of edge-nitrogen induced active sites and the hierarchical porous structure in the potassium storage performances of carbon materials.