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

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Solid polymer electrolytes (SPEs) in Zn-ion batteries (ZIBs) suffer from low ionic conductivity and limited cation transport due to polymer segment dynamics.
• This restricts the efficiency and performance of ZIBs, necessitating alternative electrolyte materials.
• Zn-based supramolecular crystals (ZMCs) show potential for improved ion conduction but their application in ZIBs remains unexplored.

Purpose of the Study:

• To develop and investigate a novel Zn-based supramolecular crystal (ZMC) as a solid-state electrolyte for Zn-ion batteries (ZIBs).
• To evaluate the ionic conductivity, Zn²⁺ transference, and electrochemical performance of the ZMC in ZIBs.
• To demonstrate the potential of ZMCs for enhancing the safety, durability, and sustainability of ZIBs.

Main Methods:

• Synthesis of a ZMC composed of succinonitrile (SN) and zinc bis(trifluoromethylsulfonyl)imide (Zn(TFSI)₂), with the formula Zn(TFSI)₂SN₃.
• Characterization of the ZMC's crystalline structure and ion conduction pathways.
• Fabrication and testing of Zn‖Zn symmetrical batteries and solid-state ZIBs using the ZMC electrolyte.

Main Results:

• The synthesized ZMC, Zn(TFSI)₂SN₃, exhibits ordered 3D tunnels facilitating high ionic conductivity (6.02×10^-4 S cm^-1 at 25°C) and a high Zn²⁺ transference number (t_Zn²⁺ = 0.97).
• Zn‖Zn symmetrical batteries with ZMC demonstrated 1200 hours of cycling stability and dendrite-free Zn plating/stripping at high areal density (3 mAh cm^-2).
• The solid-state ZIB achieved high discharge capacity (1.52 mAh cm^-2), exceptional cycling stability (83.6% retention after 70,000 cycles), wide operating temperature range (-35 to 50°C), and fast charging capability.

Conclusions:

• The developed ZMC offers a distinct structural advantage over SPEs for Zn²⁺ ion transport in solid-state ZIBs.
• ZMCs significantly improve the safety, durability, and sustainability of ZIBs by enabling efficient ion conduction and suppressing dendrite formation.
• This research highlights ZMCs as a promising next-generation electrolyte material for high-performance and reliable solid-state ZIBs.