A semi-crystalline polymer binder with enhanced electrical conductivity and strong underwater adhesion in aqueous sodium–air batteries

Abstract

Common polymer binders are insulators, which significantly diminish the battery performance owing to their low electron mobility. For aqueous sodium–air batteries (SABs) to exhibit reliable performance as energy storage systems, polymer binders should possess high electrolyte wettability, strong underwater adhesion, high crystallinity, and conductivity to efficiently transport electrons to current collectors without degradation or dissolution over time. In this study, the electrochemical performance of SABs was significantly improved using a newly developed binder containing poly(ethylene glycol), catechol, and anthracene (At) functional groups. Versatile analysis of the polymer, including two-dimensional grazing incidence-wide-angle X-ray diffraction and polarized optical microscopy, showed that the enhanced SAB performance can be attributed to the At groups which have high crystallinity due to π–π stacking, thereby lowering the resistance and increasing the electrical conductivity. Because of the catechol and PEG groups, the binder also exhibited reliable underwater adhesion, and electrolyte wettability, which are essential for aqueous SAB binders. Moreover, the binder effectively prevented carbon corrosion of the carbon current collector in the air electrode. We believe that the synthesized semi-crystalline polymer binder can be applied to various batteries to improve their electrochemical performance and stability.