Green Polymer Derived Multifunctional Layer Achieving Oriented Diffusion and Controllable Deposition of Zn2+ for Ultra-Durable Zinc-Ion Hybrid Supercapacitors

Abstract

Rampant dendrite growth and severe parasitic reactions at the electrode/electrolyte interface significantly limit the cycle life of aqueous zinc ion hybrid supercapacitors (ZHSCs). In this study, sodium lignosulfonate (SLS) as one green polymer was introduced into ZnSO₄ electrolyte to construct a multifunctional layer on the surface of Zn plates. Experimental analyses and theoretical calculations show that the presence of the SLS layer, rich in oxygen-containing functional groups (−SO₃^–), can not only modulate the structure of the electric double layer (EDL) to suppress interfacial side reactions caused by free H₂O and SO₄^2–, but also promote (101)-oriented deposition by selectively controlling the deposition behavior of Zn²⁺ through specific adsorption on different crystalline surfaces. The optimized electrolyte allows stable Zn//Zn symmetric cells to achieve a cumulative plating capacity exceeding 4 Ah cm^–2 at a high areal capacity of 5 mAh cm^–2, and stable cycling for more than 1000 cycles with an excellent average Coulombic efficiency of 99.34% in Zn//Cu asymmetric cells. The Zn//AC ZHSC exhibits ultralong cycling stability of over 40,000 cycles in the optimized electrolyte, with a capacity decay rate as low as 0.000285% per cycle.