Activating bulk S/Se/Te positive electrodes by acidic binder-induced Cu corrosion for wide-temperature Na-Chalcogen batteries.

Abstract

Sluggish kinetics and shuttle effects hinder high-energy rechargeable sodium-chalcogen batteries, requiring nanostructured positive electrodes with excess conductive additives. Here, we show that an acidic binder-induced corrosion strategy enables activity in bulk S/Se/Te positive electrodes. Carboxylic acid-rich binders create an acidic microenvironment (pH≈3) during processing, triggering spontaneous formation of copper chalcogenide interlayers on Cu current collectors. These interlayers reconstruct into active Cu₂X (X = S/Se/Te) catalysts during cycling. Using Na-Se batteries, experimental and DFT analyses confirm Cu₂Se reduces the liquid-solid conversion barrier by ~24.1% and accelerates polyselenides conversion. Polar groups in the binders enhance chemisorption, reducing the shuttling effect. Consequently, bulk Se with alginic acid binder achieves 96% theoretical utilization at 0.1 A g^‒1, rate capability of 508 mAh g^‒1 at 20 A g^‒1, stable cyclability at 5 A g^‒1 over 16,000 cycles, and low-temperature operation at 0.1 A g^‒1 (94% capacity retention at -20 °C). The strategy of transforming binders into active interface modulators provides a generalizable approach for other chalcogens, enabling practical and host-free rechargeable metal batteries with chalcogen positive electrodes.