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

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 SO42-, 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.