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 (tZn2+). 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 tZn2+ (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 (-30 to 50 °C) and fast charging ability.