Sodium Polyacrylate as a Promising Aqueous Binder of S@pPAN Cathodes for Magnesium–Sulfur Batteries

Magnesium–sulfur (Mg–S) batteries have received extensive attention due to the high theoretical energy density, low cost, high safety, and environmental friendliness. In this work, sulfurized pyrolyzed polyacrylonitrile (S@pPAN) composite is used as a cathode material of Mg–S batteries, and a comparative study on the effects of different binders on the electrochemical performance is reported for the first time. The selected binders are commercial organic-soluble poly(vinylidene fluoride) (PVDF) and water-soluble poly(ethylene oxide) (PEO), sodium polyacrylate (PAAS), locust bean gum (LBG), guar gum (GG), carboxymethyl cellulose (SCMC), and β-cyclodextrin (β-CD). The binders significantly affect the physical properties of S@pPAN electrodes and thus the electrochemical performance of the batteries. Compared to the traditional PVDF binder and other water-soluble binders, the S@pPAN electrode with an amorphous PAAS binder has better cycle stability and rate capability. The three-dimensional (3D) network formed from PAAS cross-linking improves the cohesion among the electrode constituents, and the adhesion between the electrode laminate and the current collector maintains the uniformity of electrode surface after cycling. The present work demonstrates the feasibility of using green aqueous binders to enhance the electrochemical performance of Mg–S batteries.