Regulating Zn deposition via an ion-sieving, nanoporous cellulose separator for high performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs), one of the most promising renewable energy storage devices, are largely impeded by the disreputable cycling stability in its large-scale application as a result of the undesirable Zn dendrites growth and the side reactions. In this context, a carboxylate (-COO-) anionic group functionalized cellulose nanofibrils separator (A-CNF) with nanoporous structure and ion-sieving effect is developed to realize a stable Zn anode without dendrites and by-products. An increased Zn2+ transference number and uniform Zn deposition can be achieved through the electrostatic adsorption between -COO- and Zn2+. More importantly, the synergistic effect between -COO- and hydroxyl group (-OH) in the cellulose nanofibrils separator inhibits the occurrence of side reactions caused by SO4 2-and free water molecules. As a result, the nanoporous separator consisting of carboxylated cellulose nanofibrils enables Zn anode with high stability and utilization, exhibiting a stable cycling life for 950 h in Zn//Zn cell and an admirable coulombic efficiency of 98.9 % after 300 cycles in Zn//Cu cell. The assembled Zn//MnO2 full cell with the nanoporous cellulose nanofibrils-based separator shows exceptional cyclability and capacity retention after 1000 cycles. This work provides a valuable and practical separator for high performance AZIBs, which might spur its practical application.