Nanocellulose-Enabled, All-Nanofiber, High-Performance Supercapacitor.

Nanocellulose has been used as a sustainable nanomaterial for constructing advanced electrochemical energy-storage systems with renewability, lightweight, flexibility, high performance, and satisfying safety. Here, we demonstrate a high-performance all-nanofiber asymmetric supercapacitor (ASC) assembled using a forest-based, nanocellulose-derived hierarchical porous carbon (nanocellulose carbon, HPC) anode, a mesoporous nanocellulose membrane separator (nanocellulose separator), and a NiCo2O4 cathode with nanocellulose carbon as the support matrix (nanocellulose cathode, HPC/NiCo2O4). HPC has a three-dimensional porous structure comprising interconnected nanofibers with an ultrahigh surface area of 2046 m2 g-1. When integrated with the mesoporous feature of the nanocellulose membrane separator, these properties facilitate the quick delivery of both ions and electrons even with a thick (up to several hundreds of micrometers) and highly loaded (5.8 mg cm-2) ASC design. Consequently, the all-nanofiber ASC demonstrates a high electrochemical performance (64.83 F g-1 (10.84 F cm-3) at 0.25 A g-1 and 32.78 F g-1 or 5.48 F cm-3 at 4 A g-1) that surpasses most cellulose-based ASCs ever reported. Moreover, the nanocellulose components promise renewability, low cost, and biodegradability, thereby presenting a promising direction toward high-power, environmentally friendly, and renewable energy-storage devices.