High performance Janus separator based on microstructurally controllable halloysite nanotubes for zinc-ion batteries

Zinc-ion batteries(ZIBs) are promising as the stationary energy storage owing to their inherent high safety, cost-effective, and environmental-friendly. Nevertheless, the notorious dendrite growth and water-induced side reactions on Zn anode significantly downgrade the long-lasting cycling stability and hinder the industrialization of ZIBs. Herein, a flux-homogenized Zn²⁺ transport system based on a Janus separator is constructed. This Janus separator features bacterial cellulose (BC) layer on one side and roughened halloysite nanotubes/bacterial cellulose (RHNTs/BC) layer on the other side. The abundant surface hydroxyl groups, zincophilicity sites, and ionic transmission paths of RHNTs make them ideal for acting as an ion pump to accelerate the transportation of ions, contributing to the immensely improvement of the de-solvation process, zinc deposition, and the growth of Zn dendrites. As a result, the Zn/Zn symmetrical cell with Janus separator can achieve a stable cycle life of over 800 h at 4.40 mA cm⁻². More impressively, the full cell based on Janus separator enables excellent cycling stability. This study enriches the structurally controllable construction method of HNTs and provides the fundamental theories for the application of HNTs in the field of new high-efficiency mineral energy storage materials.