Controllable construction of a 3D-honeycomb-like porous carbon network as a high-performance cathode for promoting Zn-ion storage capability†

Abstract

Inheriting the energy storage mechanism of supercapacitors and rechargeable ion batteries, zinc ion capacitors (ZICs) greatly increase their energy density at high power without sacrificing their life span. However, sluggish kinetics and insufficient active sites for Zn²⁺ storage induced by the significant mismatch of charge carriers with limited pore size hinder the efficient Zn²⁺ storage and smooth application of carbonaceous cathode materials. Herein, a three-dimensional honeycomb-like porous carbon network (HPCN) was fabricated, which can reduce the diffusion barrier for fast kinetics, produce a high-density defect area, effectively increase active sites for charge storage, and generate a high nitrogen-doping content. Benefiting from these advantages, the optimized ZICs bring out a marvelous energy/power density (130 W h kg⁻¹/11.7 kW kg⁻¹) with an ultrahigh reliable cyclability of 97.8% after 50 000 cycles at a high current density of 5 A g⁻¹. Importantly, systematic ex situ characterizations combined with theoretical calculations demonstrate that the outstanding Zn²⁺ storage capacity is attributed to the synergistic effect of physical co-adsorption of cations and reversible chemisorption. This work presents an attractive strategy for developing advanced carbon cathodes with suitable pores and accelerates the exploration of charge storage mechanisms, which may open a new avenue for practical supercapacitors.