Taking electro-chemo-mechanically synergistic effect via cholesteric cellulose crystalline interphase enables highly stable flexible zinc metal batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) are emerging as an up-and-coming energy storage technology for wearable electronics due to their intrinsic safety, cost-effectiveness, and biocompatibility. Nevertheless, the uncontrolled deposition of the Zn anode is prone to rapid short-circuit failure of ZIBs, posing a significant challenge to its practical implementation. Herein, a cholesteric structure cellulose nanocrystal (C-CNC) film that leverages the strong coordination interactions between Zn2+ ions and profuse polar functional groups on sulfonate-grafted cellulose chains, was designed as an artificial interphase layer to delicate balance between the sluggish transfer of Zn2+ ions and the faster reduction kinetics, postponing interfacial impoverishment of Zn2+. Moreover, the distinctive cholesteric structure endows the C-CNC film with exceptional mechanical robustness and functions of re-homogenizing the interfacial electric field and Zn2+ ion concentration distribution. Taking above electro-chemo-mechanically synergetic effect, the Zn interphase is stabilized due to the uniform electrodeposition behavior and suppressed side-reaction. Zn anode modified with C-CNC delivers ultralong cyclic stability up to 1000 hours and high reversibility of 99.8% average Coulombic efficiency. Consequently, the C-CNC@Zn//MnO2 cell demonstrates an excellent capacity retention of 92.0% after 1000 cycles combined with desired flexibility. Moreover, a smart wristband is fabricated to demonstrate the C-CNC films can facilitate further applications of ZIBs in wearable electronics.