Bifunctional Porous Carbon Nanofibers as Cathode Materials and Anode Protection Layers for Zinc-Ion Hybrid Supercapacitors

Zinc-ion hybrid supercapacitors (ZISCs) have attracted much attention due to their great potential for safe, high-power, and wearable energy storage but are often limited by the uncontrolled growth of zinc anode dendrites, harmful side reactions, and lower energy density. The paper proposes that hierarchical porous nitrogen-doped carbon nanofibers (HPNCFs) with tightly entangled three-dimensional (3D) networks can be prepared by the carbonization of nanoscale zeolite imidazolium ester backbone (ZIF-67) particles embedded in polyacrylonitrile via an electrostatic spinning technique. The obtained HPNCFs were used as both cathode materials and zinc anode protection layers for ZISCs. The ZISCs based on HPNCF electrodes possessed a specific capacitance of 240 F g –1 at 1 A g –1 and an energy density of 80.1 Wh kg –1 at a power density of 775.2 W kg –1, maintaining an initial capacity of 99.58% and a Coulombic efficiency of nearly 100% after 50,000 cycles. Additionally, the 3D network hierarchical porous pore structure of HPNCFs can reduce the structural stress and inhibit the growth of Zn dendrites by spatially homogenizing the flux of Zn 2+ to accelerate the ion transport rate. The HPNCFs provided corrosion protection for the zinc anodes and regulated the nucleation/growth of zinc, thus achieving a long-term stability of over 1200 h. This work provides a strategy for achieving flexible ZISCs with low cost and high performance.