Supramolecular Crystals based Fast Single Ion Conductor for Long-Cycling Solid Zinc Batteries

Abstract

The solid polymer electrolytes (SPEs) used in Zn-ion batteries (ZIBs) have low ionic conductivity due to the sluggish dynamics of polymer segments. Thus, only short-range movement of cations is supported, leading to low ionic conductivity and Zn²⁺ transference (t_Zn²⁺). Zn-based supramolecular crystals (ZMCs) have considerable potential for supporting long-distance Zn²⁺ transport; however, their efficiency in ZIBs has not been explored. The present study developed a ZMC consisting of succinonitrile (SN) and zinc bis (trifluoromethylsulfonyl) imide (Zn(TFSI)₂), with a structural formula identified as Zn(TFSI)₂SN₃. The ZMC has ordered three-dimensional tunnels in the crystalline lattices for ion conduction, providing high ionic conductivities (6.02×10⁻⁴ S cm⁻¹ at 25 °C and 3.26×10⁻⁵ S cm⁻¹ at −35 °C) and a high t_Zn²⁺ (0.97). We demonstrated that a Zn‖Zn symmetrical battery with ZMCs has long-term cycling stability (1200 h) and a dendrite-free Zn plating/stripping process, even at a high plating areal density of 3 mAh cm⁻². The as-fabricated solid-state Zn battery exhibited excellent performance, including high discharge capacity (1.52 mAh cm⁻²), long-term cycling stability (83.6 % capacity retention after 70000 cycles (7 months)), wide temperature adaptability (−35 to 50 °C) and fast charging ability. The ZMC differs from SPEs in its structure for transporting Zn²⁺ ions, significantly improving solid-state ZIBs while maintaining safety, durability, and sustainability.