Ultrathin Nitrogen‐Enriched Hybrid Carbon Nanosheets for Supercapacitors with Ultrahigh Rate Performance and High Energy Density

Abstract

AbstractTwo‐dimensional carbon nanosheets are promising materials as supercapacitor electrodes for high‐efficiency energy storage. Herein, a simple strategy is engineered to configure ultrathin nitrogen‐enriched hybrid carbon nanosheets (HCNSs) with a thickness of approximately 3.6 nm using graphene oxide as a structure‐directing agent and nano‐CaCO3 as an in‐situ‐activated agent. The polydopamine synthesized in situ on the graphene oxide sheet surface is used as a nitrogen‐rich carbon precursor, leading to the formation of nearly transparent nitrogen‐enriched HCNSs under an electron beam. Benefiting from the nitrogen‐enriched species (8.92 wt % N content), highly exposed electroactive sites and fast ion/electron transport arising from the porous and ultrathin nanosheet structure, the HCNS electrode exhibits remarkably enhanced electrochemical characteristics with a high specific capacitance of 227 F g−1 at 0.5 A g−1 and superior rate capability (70 % capacitance retention at 100 A g−1) in 6 m KOH electrolyte. More importantly, it delivers a high energy density of 86.6 W h kg−1 at a power density of 111 W kg−1 in a 1‐butyl‐3‐methylimidazolium hexafluorophosphate ionic liquid electrolyte. This study might shed new light on the configuration of nitrogen‐enriched and ultrathin 2D carbon nanomaterials for high‐efficiency energy storage/conversion devices.