Confined Polymer Electrolyte Synthesis in Porous Frameworks for Cold-Climate Zinc-Ion Batteries.

Abstract

Solid polymer electrolytes (SPEs) are vital for zinc-ion solid-state batteries (ZSSBs) for dendrite suppression but face low-temperature hurdles from poor ionic conductivity and crystallization. Here, a supramolecularly engineered SPE is constructed by in situ polymerization of 2-ethyl-2-oxazoline (EtOx) within sulfonated porous aromatic frameworks (SPAFs), acting as macroinitiators and nanoconfined reactors. Resulting poly(2-ethyl-2-oxazoline) (PEtOx) chains assemble with the SPAF via strong non-covalent interactions, forming cohesive SPAF-PEtOx (SPP) with interconnected ion transport pathways. -SO₃ ^- groups anchor Zn²⁺, while confined PEtOx chains modulate solvation dynamics, facilitating efficient Zn²⁺ migration. SPE based on SPP embedded in polyvinylidene fluoride (PVDF) matrices (SPP@PVDF) achieves high ionic conductivity (5.04 × 10^-4 s cm^-1) and a wide electrochemical window (2.74 V) at room temperature. A Zn || Zn symmetric battery exhibits stable plating/stripping over 3000 h, while a full Zn || V₂O₅ battery retains capacity over 1000 cycles at -40 °C with no decay. Notably, the ionic conductivity of SPP@PVDF at -40 °C is 8-fold higher than SPAF@PVDF, as PEtOx reduces Zn²⁺ migration barriers. This work offers a molecular-level strategy for designing cryogenically robust SPEs, advancing ZSSB technologies for extreme environments.