Physicochemical and electrochemical characterization of hybrid cellulose separators for aqueous zinc-ion batteries

Journal article, 2026

In aqueous zinc ion batteries, the use of Zn metal as the anode has been hindered by the inhomogeneous deposition of Zn and the growth of Zn structures that can pierce the separator. Here, we present a functional separator based on cellulose nanocrystals (CNC) and TEMPO-oxidized cellulose nanofibrils (TCNF) to regulate the nature of Zn deposition and thereby battery performance. The incorporation of TCNF enhances the ductility, electrolyte uptake, and ionic conductivity, while small- and wide-angle X-ray scattering (SAXS/WAXS) analysis confirms swelling of the CNC : TCNF structure when soaking in an aqueous electrolyte, but also that the swelling is limited. With an optimized weight ratio between CNC and TCNF (5 : 1), a longer cycle life at high current density (10 mA cm⁻²) and areal capacity (5 mAh cm⁻²) is achieved, compared to when a commercial filter paper separator is used. This work highlights the potential of forest biomaterials in the functionalization of separators for enhancing the cycle life of aqueous zinc ion batteries.