Dendrite-free, long cycle life Zn–MnO2 battery based on a polyanionic hydrogel electrolyte by constructing transfer channels and regulating solvation structure

Aqueous zinc ion batteries (AZIBs) are highly regarded as new generation of energy storage devices because of low cost and environmental friendliness. Particularly, flexible AZIBs with hydrogel electrolytes are suitable candidates for wearable electronics. However, continuous water-induced side reactions, uncontrolled dendrites and trade-off of electrochemical performances with mechanical strength are still obstacles for high-performance AZIBs. To address these issues, we designed a polyanionic hydrogel electrolyte (PAPHE) with sulfonate monomers and polyethylene glycol diacrylate (PEGDA) as crosslinker. Due to the electrostatic interactions between Zn 2+ and sulfonate ions, Zn 2+ can migrate along polyanionic chains. Meanwhile, electronegative oxygen atoms in PEGDA also interact with Zn 2+ and weaken electrostatic interactions. The transfer channels are formed with “wall” of polyanion chains and PEGDA. Moreover, both sulfonate ions and ether bonds on the “wall” can regulate the solvation structure to reduce the activity of water, inhibiting side reactions, corrosion or by-products. Therefore, the PAPHE shows satisfying conductivity of 16.38 mS cm −1 , stable Zn plating/stripping over 1600 h, flexibility and high compressive resistance (0.501 MPa at strain of 50 %). The Zn||PAPHE||MnO 2 cells deliver good specific capacity of 274.5 mAh g −1 and can cycle over 1800 times. The pouch-cell can also work stably under various deformations.