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

Abstract

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.