High-performance solid-state zinc-ion batteries enabled by flexible and highly Zn²⁺ conductive solid-polymer electrolyte

The utilization of solid-polymer electrolytes (SPEs) is of great interest to construct high-performance energy storage systems, owing to the high flexibility/elasticity, high thermal properties, reduced dendrite formation, suppression of cathode dissolution, and overcoming of leakage and safety issues associated with liquid electrolytes. Herein, we propose a flexible and highly Zn²⁺ conductive solid-polymer electrolyte (SPE) for solid-state zinc-ion batteries. The proposed PVA-inter-PEG_30%/IL_70% SPE exhibits high Zn²⁺ ionic conductivity (2.264 mS cm⁻¹), low glass transition temperature (T_g = −10.2 °C), good thermal stability (>200 °C), and higher oxidation stability against zinc (∼2.8 V). Moreover, PVA-inter-PEG_30%/IL_70% SPE provides a stable interfacial contact to the zinc anode and enables dendrite-free zinc stripping/platting over 3000 h of cycling at 0.2 mA cm⁻². The solid-state Zn//V₁₀O₂₄·nH₂O cell fabricated with PVA-inter-PEG_30%/IL_70% SPE delivered a discharge capacity as high as 325 mA h g⁻¹ at 0.1 A g⁻¹ and demonstrates good rate performance (∼325/110 mA h g⁻¹ at 0.1/10 A g⁻¹, respectively) with reasonable cycling stability. Besides, the PVA-inter-PEG_30%/IL_70% SPE applied in the fabrication of a flexible pouch-cell prototype demonstrates safety performance and can serve as promising and reliable energy storage devices for flexible and wearable applications.