Optimizing the sulfonic groups of a polymer to coat the zinc anode for dendrite suppression.

The zinc metal anodes in aqueous zinc-ion batteries suffer from low cycling performance caused by uncontrolled dendrite. We have designed sulfonated poly-ether-ether-ketone (SPEEK) polymers as a surface coating layer on the zinc anode for dendrite suppression, in which the sulfonic groups in polymers act as effective active sites for zinc-ion diffusion. In SPEEK, the un-sulfonated domain serves as the framework and the sulfonated domain serves as the functional part to re-distribute the zinc ions. By optimizing the degree of SPEEK sulfonation, the best zinc anode coating has been achieved to present a high reversibility of over 1600 hours in symmetric cells and improved performance in full cells.