As
electrode materials for zinc ion capacitors (ZICs), porous carbons
are an important factor affecting the electrochemical behavior of
ZICs. Heteroatom doping is an efficient approach to adjust the pore
structure, regulate the electronic structure, increase the surface
wettability, and provide pseudo capacitance. In this work, hierarchical
porous N/S codoped activated carbon (N/S-AC) materials were prepared
from lignin using urea and thiourea as the dopants. The preparation
process consisted of first step charring and second step activation
with codoping to yield N/S-AC, which exhibited hierarchical pore structure,
suitable for providing abundant active sites. The use of N/S-AC as
cathode materials for ZIC delivered an outstanding specific capacitance
of 307 F g–1 at 1 A g–1 and a
remarkable capacity retention of 99.72% after 20,000 cycles at 10
A g–1. The device also exhibited a high energy density
of 108.8 Wh kg–1 at 2880 W kg–1 and 65.8 Wh kg–1 at 115200 W kg–1. The excellent electrochemical properties were attributed to the
synergistic effect of nitrogen and sulfur elements, and hierarchical
porous structure. In sum, these findings are promising for development
of ZIC electrode materials with high energy density.