N/O co-doped hierarchical porous carbon nanosheets with enhanced Zn-ion storage capability and ultrastability

Abstract

To address the challenges of energy shortage and environmental degradation, the conversion of biomass into carbon materials is a renewable and sustainable strategy for the fabrication of Zn-ion hybrid supercapacitors (ZIHSCs) with high energy density and high power output. Herein, inspired by its intrinsic annual ring structure and N/O-containing compositions, the renewable biomass of magnolia tree branches is successfully converted into N/O co-doped hierarchical porous carbon nanosheets with cross-linked multiscale cavities, nano-sized graphene layers and optimal wettability, substantial active sites for charge entrapment, and charge transport paths for rapid kinetics, which thereby endow a coin-type ZIHSC device with marvelous energy storage capability with an ultrahigh capacity of 234.3 mA h g⁻¹ at 0.1 A g⁻¹, 105.2 mA h g⁻¹ capacity retention even at a 500-fold enlarged current density, a maximum energy of 181.6 Wh kg⁻¹ and an ultrastability with 96.9% capacity retention after 100 000 cycles at 50 A g⁻¹. Gratifyingly, the quasi-solid ZIHSC device also delivers a high capacity of 206.6 mA h g⁻¹ at 0.1 A g⁻¹ with an eminent energy density of 134.3 Wh kg⁻¹ plus remarkable anti-deformation and anti-deformation behaviors for practical application. The biomass natural property-inspired carbon synthesis strategy opens up unique perspectives on the facile conversion of biomass into advanced carbon materials for energy storage.