Directional Electron Traction and Selective-Sieving Effects Enabled by Biomimetic UIO-66-NH₂-Assisted Polyimide Electron Sponge for Ultra-Durable Sodium-Sulfur Battery

Severe sodium polysulfides (NaPSs) shuttling and sluggish reaction kinetics substantially hinder the development of room-temperature sodium-sulfur (RT/Na-S) batteries. Herein, a biomimetic uio-66-NH₂-assisted polyimide with carbon-nanotube (uio@PI/CNT) for separator-modification is proposed. Selective-sieving effects induced via the inherent PI-pore segmentation by uio-66-NH₂ efficiently inhibit NaPSs shuttling and maintain a uniform Na⁺ flux for homogeneous Na-deposition. Particularly, imide-carbonyl and triazine moieties in PI, regarded as “electron sponge” capable of successive electron uptake and supply, exert the directional electron-traction between external circuit and NaPSs to enable prompt electron-donation to and electron-extraction from NaPSs during discharging and charging, thereby remarkably reducing the sulfur-conversion energy barriers. Integrating with enhanced electron-conduction via CNT, effective binding with NaPSs, and high-speed Na⁺ transport mediated via sufficient groups synergistically provided by PI and uio-66-NH₂ for retaining active-specie and timely replenishing reactants to PI catalytic centers, the fast reaction kinetics and highly stable anode are achieved. Consequently, a high reversible capacity (1248 mAh g⁻¹) at 1 A g⁻¹ with 96.7% cycling-retention and an ultralow fading (0.0055%) per cycle even at 2 A g⁻¹ are presented. The catalytic mechanism involving “electron sponge”, with the selective-sieving effects, imparts a novel direction for exploiting the ultra-durable sodium-sulfur batteries.