Thin and strong Janus separator based on nanocellulose and Ti3C2Tx for dendrite-free aqueous zinc-ion batteries

Glass fiber separators are commonly used for aqueous zinc-ion batteries (AZIBs), whereas easily leading to Zn dendrites and parasitic reactions. Although various strategies have been proposed to address this issue, most of those modified separators still suffer from large thickness and poor mechanical properties. Herein, wheat straw-derived nanocellulose is combined with Ti3C2Tx to form a Janus separator, which is merely 32 μm in thickness and owns remarkable strength and modulus of 215.3 MPa and 8.8 GPa, respectively. In addition, the Ti3C2Tx layer brings about Maxwell–Wagner and low lattice mismatch effects, which can facilitate Zn2+ ion transfer, accelerate desolvation procedure, enhance interfacial charge transport, reduce nucleation overpotential, promote homogeneous and horizontal Zn deposition, and inhibit side reactions. With the use of such Janus separator, the Zn//Zn cell provides a high cumulative plating capacity of 2500 mAh cm−2, and the Cu//Zn cell achieves a large average Coulombic efficiency of 98.95 % over 1000 cycles. Furthermore, the Janus separator renders Zn//MnO2 battery with great rate capability and excellent cycling stability. This work offers new insights into separator modifications for AZIBs towards practical applications.