Cellulose Nanofiber-Based Separators for Durable Zn Ion Batteries

Aqueous zinc-ion batteries (ZIBs) are promising as the next-generation energy storage system due to their inherent safety and low cost, but challenges relating to H2O-induced side reactions and dendrite growth of the zinc anode are restricting its practical application. Generally, the zinc dendrites are generated by the inhomogeneous and uneven zinc deposition, which can affect the plating/stripping efficiency and even induce short circuit, thus greatly shortening the cycle lifespan and decreasing the electrochemical performance. And the side reactions are ascribed the active H2O molecules derived from the solvated Zn2+ ions, which can easily decompose into H+ and OH−, thus inducing a series of parasitic reactions and resulting in a sluggish interface kinetics. To alleviate these issues, strenuous efforts have been devoted, such as designing three-dimensional zinc anode, constructing alloyed anodes, modifying the anode-electrolyte interface, employing the “water-in-salt” electrolyte, introducing electrolyte additive, utilizing hydrogel electrolytes, and controlling exposed basal planes for zinc plating. As a key component of ZIBs, separator plays a vital role in transferring Zn2+ ions and physically separating cathode and anode, whereas the studies on separators are in infancy, implying their research value and application potential can be further explored. Herein, we develop a series of cellulose nanofiber (CNF)-based separators (CNF/GO composite separator (CG), CNF-ZrO2 composite (ZC) separator, WC-CNF (WCCNF) separator, and CNF-lithium magnesium silicate (LMS) separator (CNF+LMS)) for stable aqueous ZIBs.