Ultrahigh Nitrogen Doping of Carbon Nanosheets for High Capacity and Long Cycling Potassium Ion Storage

Abstract

Abstract Potassium‐based energy storage devices (PESDs) are promising candidates for large‐scale energy storage applications owing to potassiums abundant in nature, the low standard redox potential (−2.93 V for K/K + vs the standard hydrogen electrode) of potassium (K), and high ionic conductivity of K‐ion based electrolytes. However, lack of proper cathode and anode materials hinder practical applications of PESDs. In this work, carbon nanosheets doped with an ultrahigh content of nitrogen (22.7 at%) are successfully synthesized as an anode material for a K‐ion battery, which delivers a high capacity of 410 mAh g −1 at a current density of 500 mA g −1 , which is the best result among the carbon based anodes for PESDs. Moreover, the battery exhibits an excellent cycling performance with a capacity retention of 70% after 3000 cycles at a high current density of 5 A g −1 . In situ Raman, galvanostatic intermittent titration, and density functional theory calculations reveal that the ultrahigh N‐doped carbon nanosheet (UNCN) simultaneously combines the diffusion and pseudocapacitive mechanisms together, which remarkably improves its electrochemical performances in K‐ion storage. These results demonstrate the good potential of UNCNs as a high‐performance anode for PESDs.