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.