Biomass Acid Synergistically Regulated Hydrogel Electrolyte and Electrode-Protective Layer for Dendrite-Free Zinc-Ion...

Zinc-ion hybrid supercapacitors hold great promise for energy storage due to economic viability, environmental friendliness, and safety. However, their application is restricted by issues such as Zn dendrites, corrosion, and hydrogen evolution. Herein, a biomass acid, malic acid (MA), was used as both a hydrogel electrolyte additive and an acid etchant. By simultaneously optimizing the electrolyte component and inducing the formation of an artificial solid electrolyte interphase (SEI) layer via etching the Zn anode, significantly enhancing the stability of the Zn anode. The MA-modified hydrogel electrolyte regulates Zn2+ solvation structure and reduces Zn2+ desolvation energy, increasing the Zn2+ transference number from 0.303 to 0.598. In addition, the MA-Zn artificial SEI layer isolates the Zn anode from water, minimizing parasitic reactions and homogenizing the electric field. Based on the dual-regulation mechanism, the lifespan of a Zn anode in the Zn//Zn symmetric cell is prolonged from 82 h to over 900 h at 10 mA cm-2. Besides, the assembled zinc-ion hybrid supercapacitor exhibits a homogeneous and smooth Zn deposition layer after 5000 cycles with a capacitance retention of 87.8%. Furthermore, because the MA-modified hydrogel electrolyte demonstrates excellent mechanical flexibility and strong adhesion to the electrodes, the supercapacitor could operate reliably under multiple mechanical stresses such as bending and compression. The coordinated regulation strategy provides a promising solution for enhancing the cycling stability of zinc energy storage devices.