Hydrogel Electrolyte with High Tolerance to a Wide Spectrum of pHs and Compressive Energy Storage Devices Based on It

Abstract

Normally, hydrogel electrolytes widely used in flexible energy storage devices have limited tolerance to different pHs. Most gel electrolytes will lose their compressible capability when the adaptable pH is changed. Herein, a poly(acrylamide<inf>3</inf>-co-(sulfobetaine methacrylate)<inf>1</inf>)@polyacrylamide (P(A<inf>3</inf>-co-S<inf>1</inf>)@PAM) hydrogel electrolyte equipped with a dual crosslinking network (DN) is successfully fabricated, which exhibits excellent tolerance to any pHs, endowing various energy storage devices including batteries and supercapacitors with superior mechanical durability. The batteries with mild and alkaline P(A<inf>3</inf>-co-S<inf>1</inf>)@PAM electrolytes display superior stability (over 3000 cycles). Additionally, a Zn||MnO<inf>2</inf> battery based on the P(A<inf>3</inf>-co-S<inf>1</inf>)@PAM hydrogel electrolyte (mild) under 50% compression strain also shows excellent charge–discharge stability and high capacity at 152.4 mAh g⁻¹ after 600 cycles. The strong reversible hydrogen bonds and electrostatic forces originating from zwitterionic structures of poly(sulfobetaine methacrylate) play an important role in dissipating and dispersing energy imposed abruptly. Meanwhile, the zwitterionic structure and intermolecular NH...O-C hydrogen bonds of the hydrogel lead to the property of acid resistance and alkali resistance. The tough and robust covalent crosslinking bonds and the tight arrangement of DN polymer chains enable the hydrogel electrolytes to recover their initial shape fast once unloading.