Cellulose nanofiber enabled high-mass loading N-doped porous carbon electrode for zinc-ion supercapacitors

Zinc-ion hybrid supercapacitors (ZHSCs) are among the most promising electrochemical energy storage technologies because of their high energy density, environmental sustainability, low price, and inherent security. High-load, high-capacity cathodes are critical for the practical application of ZHSCs. However, it is challenging to achieve optimal performance of high-loading electrodes due to slow reaction kinetics, retarded ion transport, and structural instability. Herein, a salt-template technique was used to fabricate nitrogen-doped porous carbon (NPC) with large surface area, abundant mesopores, and electroactive nitrogen dopants. When combined with a fibrous network scaffold of carbon nanotubes and cellulose nanofibers (CNT/CNF), the optimized NPC delivered an outstanding specific capacitance of 133.4 mAh g−1 and a remarkable capacity retention of 95.4% after 10,000 cycles. More impressively, we achieved a cathode with high mass-loading of 10 mg cm−2 without significantly sacrificing the electrochemical performance (area capacity of 2.05 mAh cm−2 and good cycling stability with capacity retention of 86.2% after 3000 cycles). The excellent performance can be attributed to the continuous electron/ion conduction pathways of CNT/CNF scaffold and redox-active surface generated by the favorable heteroatom-doped porous carbon. In sum, this work offers a platform for making high mass-loading carbon electrodes for practical ZHSCs.